java源码学习1-集合

女爷i 2022-05-18 10:16 250阅读 0赞

public interface Collection<E> extends Iterable<E> { 
 int size();
 
 boolean isEmpty();
 
 boolean contains(Object o);
 
 Iterator<E> iterator();
 
 Object[] toArray();
 
 
 <T> T[] toArray(T[] a);
 
 
 boolean add(E e);
 
 boolean remove(Object o);
 
 boolean containsAll(Collection<?> c);
 
 boolean addAll(Collection<? extends E> c);
 
 
 boolean removeAll(Collection<?> c);
 
 
 default boolean removeIf(Predicate<? super E> filter) {
 Objects.requireNonNull(filter);
 boolean removed = false;
 final Iterator<E> each = iterator();
 while (each.hasNext()) {
 if (filter.test(each.next())) {
 each.remove();
 removed = true;
 }
 }
 return removed;
 }
 
 
 boolean retainAll(Collection<?> c);
 
 
 void clear();
 
 
 boolean equals(Object o);
 
 
 int hashCode();
 
 
 @Override
 default Spliterator<E> spliterator() {
 return Spliterators.spliterator(this, 0);
 }
 
 
 default Stream<E> stream() {
 return StreamSupport.stream(spliterator(), false);
 }
 
 
 default Stream<E> parallelStream() {
 return StreamSupport.stream(spliterator(), true);
 }
 }

public interface List<E> extends Collection<E> { 
 
 int size();
 
 boolean isEmpty();
 
 boolean contains(Object o);
 
 Iterator<E> iterator();
 
 Object[] toArray();
 
 <T> T[] toArray(T[] a);
 
 boolean add(E e);
 
 boolean remove(Object o);
 
 boolean containsAll(Collection<?> c);
 
 boolean addAll(Collection<? extends E> c);
 
 boolean addAll(int index, Collection<? extends E> c);
 
 boolean removeAll(Collection<?> c);
 
 boolean retainAll(Collection<?> c);
 
 default void replaceAll(UnaryOperator<E> operator) {
 Objects.requireNonNull(operator);
 final ListIterator<E> li = this.listIterator();
 while (li.hasNext()) {
 li.set(operator.apply(li.next()));
 }
 }
 
 @SuppressWarnings({
 "unchecked", "rawtypes"})
 default void sort(Comparator<? super E> c) {
 Object[] a = this.toArray();
 Arrays.sort(a, (Comparator) c);
 ListIterator<E> i = this.listIterator();
 for (Object e : a) {
 i.next();
 i.set((E) e);
 }
 }
 
 void clear();
 
 boolean equals(Object o);
 
 int hashCode();
 
 E get(int index);
 
 E set(int index, E element);
 
 void add(int index, E element);
 
 E remove(int index);
 
 int indexOf(Object o);
 
 int lastIndexOf(Object o);
 
 ListIterator<E> listIterator();
 
 ListIterator<E> listIterator(int index);
 
 List<E> subList(int fromIndex, int toIndex);
 
 @Override
 default Spliterator<E> spliterator() {
 return Spliterators.spliterator(this, Spliterator.ORDERED);
 }
 }

public abstract class AbstractCollection<E> implements Collection<E> { 
 /** * Sole constructor. (For invocation by subclass constructors, typically * implicit.) */
 protected AbstractCollection() {
 }
 
 // Query Operations
 
 /** * Returns an iterator over the elements contained in this collection. * * @return an iterator over the elements contained in this collection */
 public abstract Iterator<E> iterator();
 
 public abstract int size();
 
 /** * { @inheritDoc} * * This implementation returns <tt>size() == 0</tt>. */
 public boolean isEmpty() {
 return size() == 0;
 }
 
 /** * { @inheritDoc} * * This implementation iterates over the elements in the collection, * checking each element in turn for equality with the specified element. * * @throws ClassCastException { @inheritDoc} * @throws NullPointerException { @inheritDoc} */
 public boolean contains(Object o) {
 Iterator<E> it = iterator();
 if (o==null) {
 while (it.hasNext())
 if (it.next()==null)
 return true;
 } else {
 while (it.hasNext())
 if (o.equals(it.next()))
 return true;
 }
 return false;
 }
 
 /** * { @inheritDoc} * * This implementation returns an array containing all the elements * returned by this collection's iterator, in the same order, stored in * consecutive elements of the array, starting with index { @code 0}. * The length of the returned array is equal to the number of elements * returned by the iterator, even if the size of this collection changes * during iteration, as might happen if the collection permits * concurrent modification during iteration. The { @code size} method is * called only as an optimization hint; the correct result is returned * even if the iterator returns a different number of elements. * * This method is equivalent to: * * <pre> { @code * List<E> list = new ArrayList<E>(size()); * for (E e : this) * list.add(e); * return list.toArray(); * }</pre> */
 public Object[] toArray() {
 // Estimate size of array; be prepared to see more or fewer elements
 Object[] r = new Object[size()];
 Iterator<E> it = iterator();
 for (int i = 0; i < r.length; i++) {
 if (! it.hasNext()) // fewer elements than expected
 return Arrays.copyOf(r, i);
 r[i] = it.next();
 }
 return it.hasNext() ? finishToArray(r, it) : r;
 }
 
 /** * { @inheritDoc} * * This implementation returns an array containing all the elements * returned by this collection's iterator in the same order, stored in * consecutive elements of the array, starting with index { @code 0}. * If the number of elements returned by the iterator is too large to * fit into the specified array, then the elements are returned in a * newly allocated array with length equal to the number of elements * returned by the iterator, even if the size of this collection * changes during iteration, as might happen if the collection permits * concurrent modification during iteration. The { @code size} method is * called only as an optimization hint; the correct result is returned * even if the iterator returns a different number of elements. * * This method is equivalent to: * * <pre> { @code * List<E> list = new ArrayList<E>(size()); * for (E e : this) * list.add(e); * return list.toArray(a); * }</pre> * * @throws ArrayStoreException { @inheritDoc} * @throws NullPointerException { @inheritDoc} */
 @SuppressWarnings("unchecked")
 public <T> T[] toArray(T[] a) {
 // Estimate size of array; be prepared to see more or fewer elements
 int size = size();
 T[] r = a.length >= size ? a :
 (T[])java.lang.reflect.Array
 .newInstance(a.getClass().getComponentType(), size);
 Iterator<E> it = iterator();
 
 for (int i = 0; i < r.length; i++) {
 if (! it.hasNext()) { // fewer elements than expected
 if (a == r) {
 r[i] = null; // null-terminate
 } else if (a.length < i) {
 return Arrays.copyOf(r, i);
 } else {
 System.arraycopy(r, 0, a, 0, i);
 if (a.length > i) {
 a[i] = null;
 }
 }
 return a;
 }
 r[i] = (T)it.next();
 }
 // more elements than expected
 return it.hasNext() ? finishToArray(r, it) : r;
 }
 
 /** * The maximum size of array to allocate. * Some VMs reserve some header words in an array. * Attempts to allocate larger arrays may result in * OutOfMemoryError: Requested array size exceeds VM limit */
 private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
 
 /** * Reallocates the array being used within toArray when the iterator * returned more elements than expected, and finishes filling it from * the iterator. * * @param r the array, replete with previously stored elements * @param it the in-progress iterator over this collection * @return array containing the elements in the given array, plus any * further elements returned by the iterator, trimmed to size */
 @SuppressWarnings("unchecked")
 private static <T> T[] finishToArray(T[] r, Iterator<?> it) {
 int i = r.length;
 while (it.hasNext()) {
 int cap = r.length;
 if (i == cap) {
 int newCap = cap + (cap >> 1) + 1;
 // overflow-conscious code
 if (newCap - MAX_ARRAY_SIZE > 0)
 newCap = hugeCapacity(cap + 1);
 r = Arrays.copyOf(r, newCap);
 }
 r[i++] = (T)it.next();
 }
 // trim if overallocated
 return (i == r.length) ? r : Arrays.copyOf(r, i);
 }
 
 private static int hugeCapacity(int minCapacity) {
 if (minCapacity < 0) // overflow
 throw new OutOfMemoryError
 ("Required array size too large");
 return (minCapacity > MAX_ARRAY_SIZE) ?
 Integer.MAX_VALUE :
 MAX_ARRAY_SIZE;
 }
 
 // Modification Operations
 
 /** * { @inheritDoc} * * This implementation always throws an * <tt>UnsupportedOperationException</tt>. * * @throws UnsupportedOperationException { @inheritDoc} * @throws ClassCastException { @inheritDoc} * @throws NullPointerException { @inheritDoc} * @throws IllegalArgumentException { @inheritDoc} * @throws IllegalStateException { @inheritDoc} */
 public boolean add(E e) {
 throw new UnsupportedOperationException();
 }
 
 /** * { @inheritDoc} * * This implementation iterates over the collection looking for the * specified element. If it finds the element, it removes the element * from the collection using the iterator's remove method. * * Note that this implementation throws an * <tt>UnsupportedOperationException</tt> if the iterator returned by this * collection's iterator method does not implement the <tt>remove</tt> * method and this collection contains the specified object. * * @throws UnsupportedOperationException { @inheritDoc} * @throws ClassCastException { @inheritDoc} * @throws NullPointerException { @inheritDoc} */
 public boolean remove(Object o) {
 Iterator<E> it = iterator();
 if (o==null) {
 while (it.hasNext()) {
 if (it.next()==null) {
 it.remove();
 return true;
 }
 }
 } else {
 while (it.hasNext()) {
 if (o.equals(it.next())) {
 it.remove();
 return true;
 }
 }
 }
 return false;
 }
 
 
 // Bulk Operations
 
 /** * { @inheritDoc} * * This implementation iterates over the specified collection, * checking each element returned by the iterator in turn to see * if it's contained in this collection. If all elements are so * contained <tt>true</tt> is returned, otherwise <tt>false</tt>. * * @throws ClassCastException { @inheritDoc} * @throws NullPointerException { @inheritDoc} * @see #contains(Object) */
 public boolean containsAll(Collection<?> c) {
 for (Object e : c)
 if (!contains(e))
 return false;
 return true;
 }
 
 /** * { @inheritDoc} * * This implementation iterates over the specified collection, and adds * each object returned by the iterator to this collection, in turn. * * Note that this implementation will throw an * <tt>UnsupportedOperationException</tt> unless <tt>add</tt> is * overridden (assuming the specified collection is non-empty). * * @throws UnsupportedOperationException { @inheritDoc} * @throws ClassCastException { @inheritDoc} * @throws NullPointerException { @inheritDoc} * @throws IllegalArgumentException { @inheritDoc} * @throws IllegalStateException { @inheritDoc} * * @see #add(Object) */
 public boolean addAll(Collection<? extends E> c) {
 boolean modified = false;
 for (E e : c)
 if (add(e))
 modified = true;
 return modified;
 }
 
 /** * { @inheritDoc} * * This implementation iterates over this collection, checking each * element returned by the iterator in turn to see if it's contained * in the specified collection. If it's so contained, it's removed from * this collection with the iterator's <tt>remove</tt> method. * * Note that this implementation will throw an * <tt>UnsupportedOperationException</tt> if the iterator returned by the * <tt>iterator</tt> method does not implement the <tt>remove</tt> method * and this collection contains one or more elements in common with the * specified collection. * * @throws UnsupportedOperationException { @inheritDoc} * @throws ClassCastException { @inheritDoc} * @throws NullPointerException { @inheritDoc} * * @see #remove(Object) * @see #contains(Object) */
 public boolean removeAll(Collection<?> c) {
 Objects.requireNonNull(c);
 boolean modified = false;
 Iterator<?> it = iterator();
 while (it.hasNext()) {
 if (c.contains(it.next())) {
 it.remove();
 modified = true;
 }
 }
 return modified;
 }
 
 /** * { @inheritDoc} * * This implementation iterates over this collection, checking each * element returned by the iterator in turn to see if it's contained * in the specified collection. If it's not so contained, it's removed * from this collection with the iterator's <tt>remove</tt> method. * * Note that this implementation will throw an * <tt>UnsupportedOperationException</tt> if the iterator returned by the * <tt>iterator</tt> method does not implement the <tt>remove</tt> method * and this collection contains one or more elements not present in the * specified collection. * * @throws UnsupportedOperationException { @inheritDoc} * @throws ClassCastException { @inheritDoc} * @throws NullPointerException { @inheritDoc} * * @see #remove(Object) * @see #contains(Object) */
 public boolean retainAll(Collection<?> c) {
 Objects.requireNonNull(c);
 boolean modified = false;
 Iterator<E> it = iterator();
 while (it.hasNext()) {
 if (!c.contains(it.next())) {
 it.remove();
 modified = true;
 }
 }
 return modified;
 }
 
 /** * { @inheritDoc} * * This implementation iterates over this collection, removing each * element using the <tt>Iterator.remove</tt> operation. Most * implementations will probably choose to override this method for * efficiency. * * Note that this implementation will throw an * <tt>UnsupportedOperationException</tt> if the iterator returned by this * collection's <tt>iterator</tt> method does not implement the * <tt>remove</tt> method and this collection is non-empty. * * @throws UnsupportedOperationException { @inheritDoc} */
 public void clear() {
 Iterator<E> it = iterator();
 while (it.hasNext()) {
 it.next();
 it.remove();
 }
 }
 
 
 // String conversion
 
 /** * Returns a string representation of this collection. The string * representation consists of a list of the collection's elements in the * order they are returned by its iterator, enclosed in square brackets * (<tt>"[]"</tt>). Adjacent elements are separated by the characters * <tt>", "</tt> (comma and space). Elements are converted to strings as * by { @link String#valueOf(Object)}. * * @return a string representation of this collection */
 public String toString() {
 Iterator<E> it = iterator();
 if (! it.hasNext())
 return "[]";
 
 StringBuilder sb = new StringBuilder();
 sb.append('[');
 for (;;) {
 E e = it.next();
 sb.append(e == this ? "(this Collection)" : e);
 if (! it.hasNext())
 return sb.append(']').toString();
 sb.append(',').append(' ');
 }
 }
 
 }

--------------------

package java.util;
 
 
 
 public abstract class AbstractList<E> extends AbstractCollection<E> implements List<E> { 
 /** * Sole constructor. (For invocation by subclass constructors, typically * implicit.) */
 protected AbstractList() {
 }
 
 /** * Appends the specified element to the end of this list (optional * operation). * * Lists that support this operation may place limitations on what * elements may be added to this list. In particular, some * lists will refuse to add null elements, and others will impose * restrictions on the type of elements that may be added. List * classes should clearly specify in their documentation any restrictions * on what elements may be added. * * This implementation calls { @code add(size(), e)}. * * Note that this implementation throws an * { @code UnsupportedOperationException} unless * { @link #add(int, Object) add(int, E)} is overridden. * * @param e element to be appended to this list * @return { @code true} (as specified by { @link Collection#add}) * @throws UnsupportedOperationException if the { @code add} operation * is not supported by this list * @throws ClassCastException if the class of the specified element * prevents it from being added to this list * @throws NullPointerException if the specified element is null and this * list does not permit null elements * @throws IllegalArgumentException if some property of this element * prevents it from being added to this list */
 public boolean add(E e) {
 add(size(), e);
 return true;
 }
 
 /** * { @inheritDoc} * * @throws IndexOutOfBoundsException { @inheritDoc} */
 abstract public E get(int index);
 
 /** * { @inheritDoc} * * This implementation always throws an * { @code UnsupportedOperationException}. * * @throws UnsupportedOperationException { @inheritDoc} * @throws ClassCastException { @inheritDoc} * @throws NullPointerException { @inheritDoc} * @throws IllegalArgumentException { @inheritDoc} * @throws IndexOutOfBoundsException { @inheritDoc} */
 public E set(int index, E element) {
 throw new UnsupportedOperationException();
 }
 
 /** * { @inheritDoc} * * This implementation always throws an * { @code UnsupportedOperationException}. * * @throws UnsupportedOperationException { @inheritDoc} * @throws ClassCastException { @inheritDoc} * @throws NullPointerException { @inheritDoc} * @throws IllegalArgumentException { @inheritDoc} * @throws IndexOutOfBoundsException { @inheritDoc} */
 public void add(int index, E element) {
 throw new UnsupportedOperationException();
 }
 
 /** * { @inheritDoc} * * This implementation always throws an * { @code UnsupportedOperationException}. * * @throws UnsupportedOperationException { @inheritDoc} * @throws IndexOutOfBoundsException { @inheritDoc} */
 public E remove(int index) {
 throw new UnsupportedOperationException();
 }
 
 
 // Search Operations
 
 /** * { @inheritDoc} * * This implementation first gets a list iterator (with * { @code listIterator()}). Then, it iterates over the list until the * specified element is found or the end of the list is reached. * * @throws ClassCastException { @inheritDoc} * @throws NullPointerException { @inheritDoc} */
 public int indexOf(Object o) {
 ListIterator<E> it = listIterator();
 if (o==null) {
 while (it.hasNext())
 if (it.next()==null)
 return it.previousIndex();
 } else {
 while (it.hasNext())
 if (o.equals(it.next()))
 return it.previousIndex();
 }
 return -1;
 }
 
 /** * { @inheritDoc} * * This implementation first gets a list iterator that points to the end * of the list (with { @code listIterator(size())}). Then, it iterates * backwards over the list until the specified element is found, or the * beginning of the list is reached. * * @throws ClassCastException { @inheritDoc} * @throws NullPointerException { @inheritDoc} */
 public int lastIndexOf(Object o) {
 ListIterator<E> it = listIterator(size());
 if (o==null) {
 while (it.hasPrevious())
 if (it.previous()==null)
 return it.nextIndex();
 } else {
 while (it.hasPrevious())
 if (o.equals(it.previous()))
 return it.nextIndex();
 }
 return -1;
 }
 
 
 // Bulk Operations
 
 /** * Removes all of the elements from this list (optional operation). * The list will be empty after this call returns. * * This implementation calls { @code removeRange(0, size())}. * * Note that this implementation throws an * { @code UnsupportedOperationException} unless { @code remove(int * index)} or { @code removeRange(int fromIndex, int toIndex)} is * overridden. * * @throws UnsupportedOperationException if the { @code clear} operation * is not supported by this list */
 public void clear() {
 removeRange(0, size());
 }
 
 /** * { @inheritDoc} * * This implementation gets an iterator over the specified collection * and iterates over it, inserting the elements obtained from the * iterator into this list at the appropriate position, one at a time, * using { @code add(int, E)}. * Many implementations will override this method for efficiency. * * Note that this implementation throws an * { @code UnsupportedOperationException} unless * { @link #add(int, Object) add(int, E)} is overridden. * * @throws UnsupportedOperationException { @inheritDoc} * @throws ClassCastException { @inheritDoc} * @throws NullPointerException { @inheritDoc} * @throws IllegalArgumentException { @inheritDoc} * @throws IndexOutOfBoundsException { @inheritDoc} */
 public boolean addAll(int index, Collection<? extends E> c) {
 rangeCheckForAdd(index);
 boolean modified = false;
 for (E e : c) {
 add(index++, e);
 modified = true;
 }
 return modified;
 }
 
 
 // Iterators
 
 /** * Returns an iterator over the elements in this list in proper sequence. * * This implementation returns a straightforward implementation of the * iterator interface, relying on the backing list's { @code size()}, * { @code get(int)}, and { @code remove(int)} methods. * * Note that the iterator returned by this method will throw an * { @link UnsupportedOperationException} in response to its * { @code remove} method unless the list's { @code remove(int)} method is * overridden. * * This implementation can be made to throw runtime exceptions in the * face of concurrent modification, as described in the specification * for the (protected) { @link #modCount} field. * * @return an iterator over the elements in this list in proper sequence */
 public Iterator<E> iterator() {
 return new Itr();
 }
 
 /** * { @inheritDoc} * * This implementation returns { @code listIterator(0)}. * * @see #listIterator(int) */
 public ListIterator<E> listIterator() {
 return listIterator(0);
 }
 
 /** * { @inheritDoc} * * This implementation returns a straightforward implementation of the * { @code ListIterator} interface that extends the implementation of the * { @code Iterator} interface returned by the { @code iterator()} method. * The { @code ListIterator} implementation relies on the backing list's * { @code get(int)}, { @code set(int, E)}, { @code add(int, E)} * and { @code remove(int)} methods. * * Note that the list iterator returned by this implementation will * throw an { @link UnsupportedOperationException} in response to its * { @code remove}, { @code set} and { @code add} methods unless the * list's { @code remove(int)}, { @code set(int, E)}, and * { @code add(int, E)} methods are overridden. * * This implementation can be made to throw runtime exceptions in the * face of concurrent modification, as described in the specification for * the (protected) { @link #modCount} field. * * @throws IndexOutOfBoundsException { @inheritDoc} */
 public ListIterator<E> listIterator(final int index) {
 rangeCheckForAdd(index);
 
 return new ListItr(index);
 }
 
 private class Itr implements Iterator<E> { 
 /** * Index of element to be returned by subsequent call to next. */
 int cursor = 0;
 
 /** * Index of element returned by most recent call to next or * previous. Reset to -1 if this element is deleted by a call * to remove. */
 int lastRet = -1;
 
 /** * The modCount value that the iterator believes that the backing * List should have. If this expectation is violated, the iterator * has detected concurrent modification. */
 int expectedModCount = modCount;
 
 public boolean hasNext() {
 return cursor != size();
 }
 
 public E next() {
 checkForComodification();
 try {
 int i = cursor;
 E next = get(i);
 lastRet = i;
 cursor = i + 1;
 return next;
 } catch (IndexOutOfBoundsException e) {
 checkForComodification();
 throw new NoSuchElementException();
 }
 }
 
 public void remove() {
 if (lastRet < 0)
 throw new IllegalStateException();
 checkForComodification();
 
 try {
 AbstractList.this.remove(lastRet);
 if (lastRet < cursor)
 cursor--;
 lastRet = -1;
 expectedModCount = modCount;
 } catch (IndexOutOfBoundsException e) {
 throw new ConcurrentModificationException();
 }
 }
 
 final void checkForComodification() {
 if (modCount != expectedModCount)
 throw new ConcurrentModificationException();
 }
 }
 
 private class ListItr extends Itr implements ListIterator<E> { 
 ListItr(int index) {
 cursor = index;
 }
 
 public boolean hasPrevious() {
 return cursor != 0;
 }
 
 public E previous() {
 checkForComodification();
 try {
 int i = cursor - 1;
 E previous = get(i);
 lastRet = cursor = i;
 return previous;
 } catch (IndexOutOfBoundsException e) {
 checkForComodification();
 throw new NoSuchElementException();
 }
 }
 
 public int nextIndex() {
 return cursor;
 }
 
 public int previousIndex() {
 return cursor-1;
 }
 
 public void set(E e) {
 if (lastRet < 0)
 throw new IllegalStateException();
 checkForComodification();
 
 try {
 AbstractList.this.set(lastRet, e);
 expectedModCount = modCount;
 } catch (IndexOutOfBoundsException ex) {
 throw new ConcurrentModificationException();
 }
 }
 
 public void add(E e) {
 checkForComodification();
 
 try {
 int i = cursor;
 AbstractList.this.add(i, e);
 lastRet = -1;
 cursor = i + 1;
 expectedModCount = modCount;
 } catch (IndexOutOfBoundsException ex) {
 throw new ConcurrentModificationException();
 }
 }
 }
 
 /** * { @inheritDoc} * * This implementation returns a list that subclasses * { @code AbstractList}. The subclass stores, in private fields, the * offset of the subList within the backing list, the size of the subList * (which can change over its lifetime), and the expected * { @code modCount} value of the backing list. There are two variants * of the subclass, one of which implements { @code RandomAccess}. * If this list implements { @code RandomAccess} the returned list will * be an instance of the subclass that implements { @code RandomAccess}. * * The subclass's { @code set(int, E)}, { @code get(int)}, * { @code add(int, E)}, { @code remove(int)}, { @code addAll(int, * Collection)} and { @code removeRange(int, int)} methods all * delegate to the corresponding methods on the backing abstract list, * after bounds-checking the index and adjusting for the offset. The * { @code addAll(Collection c)} method merely returns { @code addAll(size, * c)}. * * The { @code listIterator(int)} method returns a "wrapper object" * over a list iterator on the backing list, which is created with the * corresponding method on the backing list. The { @code iterator} method * merely returns { @code listIterator()}, and the { @code size} method * merely returns the subclass's { @code size} field. * * All methods first check to see if the actual { @code modCount} of * the backing list is equal to its expected value, and throw a * { @code ConcurrentModificationException} if it is not. * * @throws IndexOutOfBoundsException if an endpoint index value is out of range * { @code (fromIndex < 0 || toIndex > size)} * @throws IllegalArgumentException if the endpoint indices are out of order * { @code (fromIndex > toIndex)} */
 public List<E> subList(int fromIndex, int toIndex) {
 return (this instanceof RandomAccess ?
 new RandomAccessSubList<>(this, fromIndex, toIndex) :
 new SubList<>(this, fromIndex, toIndex));
 }
 
 // Comparison and hashing
 
 /** * Compares the specified object with this list for equality. Returns * { @code true} if and only if the specified object is also a list, both * lists have the same size, and all corresponding pairs of elements in * the two lists are equal. (Two elements { @code e1} and * { @code e2} are equal if { @code (e1==null ? e2==null : * e1.equals(e2))}.) In other words, two lists are defined to be * equal if they contain the same elements in the same order. * * This implementation first checks if the specified object is this * list. If so, it returns { @code true}; if not, it checks if the * specified object is a list. If not, it returns { @code false}; if so, * it iterates over both lists, comparing corresponding pairs of elements. * If any comparison returns { @code false}, this method returns * { @code false}. If either iterator runs out of elements before the * other it returns { @code false} (as the lists are of unequal length); * otherwise it returns { @code true} when the iterations complete. * * @param o the object to be compared for equality with this list * @return { @code true} if the specified object is equal to this list */
 public boolean equals(Object o) {
 if (o == this)
 return true;
 if (!(o instanceof List))
 return false;
 
 ListIterator<E> e1 = listIterator();
 ListIterator<?> e2 = ((List<?>) o).listIterator();
 while (e1.hasNext() && e2.hasNext()) {
 E o1 = e1.next();
 Object o2 = e2.next();
 if (!(o1==null ? o2==null : o1.equals(o2)))
 return false;
 }
 return !(e1.hasNext() || e2.hasNext());
 }
 
 /** * Returns the hash code value for this list. * * This implementation uses exactly the code that is used to define the * list hash function in the documentation for the { @link List#hashCode} * method. * * @return the hash code value for this list */
 public int hashCode() {
 int hashCode = 1;
 for (E e : this)
 hashCode = 31*hashCode + (e==null ? 0 : e.hashCode());
 return hashCode;
 }
 
 /** * Removes from this list all of the elements whose index is between * { @code fromIndex}, inclusive, and { @code toIndex}, exclusive. * Shifts any succeeding elements to the left (reduces their index). * This call shortens the list by { @code (toIndex - fromIndex)} elements. * (If { @code toIndex==fromIndex}, this operation has no effect.) * * This method is called by the { @code clear} operation on this list * and its subLists. Overriding this method to take advantage of * the internals of the list implementation can substantially * improve the performance of the { @code clear} operation on this list * and its subLists. * * This implementation gets a list iterator positioned before * { @code fromIndex}, and repeatedly calls { @code ListIterator.next} * followed by { @code ListIterator.remove} until the entire range has * been removed. Note: if { @code ListIterator.remove} requires linear * time, this implementation requires quadratic time. * * @param fromIndex index of first element to be removed * @param toIndex index after last element to be removed */
 protected void removeRange(int fromIndex, int toIndex) {
 ListIterator<E> it = listIterator(fromIndex);
 for (int i=0, n=toIndex-fromIndex; i<n; i++) {
 it.next();
 it.remove();
 }
 }
 
 /** * The number of times this list has been structurally modified. * Structural modifications are those that change the size of the * list, or otherwise perturb it in such a fashion that iterations in * progress may yield incorrect results. * * This field is used by the iterator and list iterator implementation * returned by the { @code iterator} and { @code listIterator} methods. * If the value of this field changes unexpectedly, the iterator (or list * iterator) will throw a { @code ConcurrentModificationException} in * response to the { @code next}, { @code remove}, { @code previous}, * { @code set} or { @code add} operations. This provides * fail-fast behavior, rather than non-deterministic behavior in * the face of concurrent modification during iteration. * * Use of this field by subclasses is optional. If a subclass * wishes to provide fail-fast iterators (and list iterators), then it * merely has to increment this field in its { @code add(int, E)} and * { @code remove(int)} methods (and any other methods that it overrides * that result in structural modifications to the list). A single call to * { @code add(int, E)} or { @code remove(int)} must add no more than * one to this field, or the iterators (and list iterators) will throw * bogus { @code ConcurrentModificationExceptions}. If an implementation * does not wish to provide fail-fast iterators, this field may be * ignored. */
 protected transient int modCount = 0;
 
 private void rangeCheckForAdd(int index) {
 if (index < 0 || index > size())
 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
 }
 
 private String outOfBoundsMsg(int index) {
 return "Index: "+index+", Size: "+size();
 }
 }
 
 class SubList<E> extends AbstractList<E> { 
 private final AbstractList<E> l;
 private final int offset;
 private int size;
 
 SubList(AbstractList<E> list, int fromIndex, int toIndex) {
 if (fromIndex < 0)
 throw new IndexOutOfBoundsException("fromIndex = " + fromIndex);
 if (toIndex > list.size())
 throw new IndexOutOfBoundsException("toIndex = " + toIndex);
 if (fromIndex > toIndex)
 throw new IllegalArgumentException("fromIndex(" + fromIndex +
 ") > toIndex(" + toIndex + ")");
 l = list;
 offset = fromIndex;
 size = toIndex - fromIndex;
 this.modCount = l.modCount;
 }
 
 public E set(int index, E element) {
 rangeCheck(index);
 checkForComodification();
 return l.set(index+offset, element);
 }
 
 public E get(int index) {
 rangeCheck(index);
 checkForComodification();
 return l.get(index+offset);
 }
 
 public int size() {
 checkForComodification();
 return size;
 }
 
 public void add(int index, E element) {
 rangeCheckForAdd(index);
 checkForComodification();
 l.add(index+offset, element);
 this.modCount = l.modCount;
 size++;
 }
 
 public E remove(int index) {
 rangeCheck(index);
 checkForComodification();
 E result = l.remove(index+offset);
 this.modCount = l.modCount;
 size--;
 return result;
 }
 
 protected void removeRange(int fromIndex, int toIndex) {
 checkForComodification();
 l.removeRange(fromIndex+offset, toIndex+offset);
 this.modCount = l.modCount;
 size -= (toIndex-fromIndex);
 }
 
 public boolean addAll(Collection<? extends E> c) {
 return addAll(size, c);
 }
 
 public boolean addAll(int index, Collection<? extends E> c) {
 rangeCheckForAdd(index);
 int cSize = c.size();
 if (cSize==0)
 return false;
 
 checkForComodification();
 l.addAll(offset+index, c);
 this.modCount = l.modCount;
 size += cSize;
 return true;
 }
 
 public Iterator<E> iterator() {
 return listIterator();
 }
 
 public ListIterator<E> listIterator(final int index) {
 checkForComodification();
 rangeCheckForAdd(index);
 
 return new ListIterator<E>() {
 private final ListIterator<E> i = l.listIterator(index+offset);
 
 public boolean hasNext() {
 return nextIndex() < size;
 }
 
 public E next() {
 if (hasNext())
 return i.next();
 else
 throw new NoSuchElementException();
 }
 
 public boolean hasPrevious() {
 return previousIndex() >= 0;
 }
 
 public E previous() {
 if (hasPrevious())
 return i.previous();
 else
 throw new NoSuchElementException();
 }
 
 public int nextIndex() {
 return i.nextIndex() - offset;
 }
 
 public int previousIndex() {
 return i.previousIndex() - offset;
 }
 
 public void remove() {
 i.remove();
 SubList.this.modCount = l.modCount;
 size--;
 }
 
 public void set(E e) {
 i.set(e);
 }
 
 public void add(E e) {
 i.add(e);
 SubList.this.modCount = l.modCount;
 size++;
 }
 };
 }
 
 public List<E> subList(int fromIndex, int toIndex) {
 return new SubList<>(this, fromIndex, toIndex);
 }
 
 private void rangeCheck(int index) {
 if (index < 0 || index >= size)
 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
 }
 
 private void rangeCheckForAdd(int index) {
 if (index < 0 || index > size)
 throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
 }
 
 private String outOfBoundsMsg(int index) {
 return "Index: "+index+", Size: "+size;
 }
 
 private void checkForComodification() {
 if (this.modCount != l.modCount)
 throw new ConcurrentModificationException();
 }
 }
 
 class RandomAccessSubList<E> extends SubList<E> implements RandomAccess { 
 RandomAccessSubList(AbstractList<E> list, int fromIndex, int toIndex) {
 super(list, fromIndex, toIndex);
 }
 
 public List<E> subList(int fromIndex, int toIndex) {
 return new RandomAccessSubList<>(this, fromIndex, toIndex);
 }
 }

package java.util; import java.util.function.Consumer; import java.util.function.Predicate; import java.util.function.UnaryOperator; import sun.misc.SharedSecrets; public class ArrayList<E> extends AbstractList<E> implements List<E>, RandomAccess, Cloneable, java.io.Serializable { private static final long serialVersionUID = 8683452581122892189L; /** * Default initial capacity. */ private static final int DEFAULT_CAPACITY = 10; /** * Shared empty array instance used for empty instances. */ private static final Object[] EMPTY_ELEMENTDATA = {}; /** * Shared empty array instance used for default sized empty instances. We * distinguish this from EMPTY_ELEMENTDATA to know how much to inflate when * first element is added. */ private static final Object[] DEFAULTCAPACITY_EMPTY_ELEMENTDATA = {}; /** * The array buffer into which the elements of the ArrayList are stored. * The capacity of the ArrayList is the length of this array buffer. Any * empty ArrayList with elementData == DEFAULTCAPACITY_EMPTY_ELEMENTDATA * will be expanded to DEFAULT_CAPACITY when the first element is added. */ transient Object[] elementData; // non-private to simplify nested class access /** * The size of the ArrayList (the number of elements it contains). * * @serial */ private int size; /** * Constructs an empty list with the specified initial capacity. * * @param initialCapacity the initial capacity of the list * @throws IllegalArgumentException if the specified initial capacity * is negative */ public ArrayList(int initialCapacity) { if (initialCapacity > 0) { this.elementData = new Object[initialCapacity]; } else if (initialCapacity == 0) { this.elementData = EMPTY_ELEMENTDATA; } else { throw new IllegalArgumentException("Illegal Capacity: "+ initialCapacity); } } /** * Constructs an empty list with an initial capacity of ten. */ public ArrayList() { this.elementData = DEFAULTCAPACITY_EMPTY_ELEMENTDATA; } /** * Constructs a list containing the elements of the specified * collection, in the order they are returned by the collection's * iterator. * * @param c the collection whose elements are to be placed into this list * @throws NullPointerException if the specified collection is null */ public ArrayList(Collection<? extends E> c) { elementData = c.toArray(); if ((size = elementData.length) != 0) { // c.toArray might (incorrectly) not return Object[] (see 6260652) if (elementData.getClass() != Object[].class) elementData = Arrays.copyOf(elementData, size, Object[].class); } else { // replace with empty array. this.elementData = EMPTY_ELEMENTDATA; } } /** * Trims the capacity of this <tt>ArrayList</tt> instance to be the * list's current size. An application can use this operation to minimize * the storage of an <tt>ArrayList</tt> instance. */ public void trimToSize() { modCount++; if (size < elementData.length) { elementData = (size == 0) ? EMPTY_ELEMENTDATA : Arrays.copyOf(elementData, size); } } /** * Increases the capacity of this <tt>ArrayList</tt> instance, if * necessary, to ensure that it can hold at least the number of elements * specified by the minimum capacity argument. * * @param minCapacity the desired minimum capacity */ public void ensureCapacity(int minCapacity) { int minExpand = (elementData != DEFAULTCAPACITY_EMPTY_ELEMENTDATA) // any size if not default element table ? 0 // larger than default for default empty table. It's already // supposed to be at default size. : DEFAULT_CAPACITY; if (minCapacity > minExpand) { ensureExplicitCapacity(minCapacity); } } private static int calculateCapacity(Object[] elementData, int minCapacity) { if (elementData == DEFAULTCAPACITY_EMPTY_ELEMENTDATA) { return Math.max(DEFAULT_CAPACITY, minCapacity); } return minCapacity; } private void ensureCapacityInternal(int minCapacity) { ensureExplicitCapacity(calculateCapacity(elementData, minCapacity)); } private void ensureExplicitCapacity(int minCapacity) { modCount++; // overflow-conscious code if (minCapacity - elementData.length > 0) grow(minCapacity); } /** * The maximum size of array to allocate. * Some VMs reserve some header words in an array. * Attempts to allocate larger arrays may result in * OutOfMemoryError: Requested array size exceeds VM limit */ private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8; /** * Increases the capacity to ensure that it can hold at least the * number of elements specified by the minimum capacity argument. * * @param minCapacity the desired minimum capacity */ private void grow(int minCapacity) { // overflow-conscious code int oldCapacity = elementData.length; int newCapacity = oldCapacity + (oldCapacity >> 1); if (newCapacity - minCapacity < 0) newCapacity = minCapacity; if (newCapacity - MAX_ARRAY_SIZE > 0) newCapacity = hugeCapacity(minCapacity); // minCapacity is usually close to size, so this is a win: elementData = Arrays.copyOf(elementData, newCapacity); } private static int hugeCapacity(int minCapacity) { if (minCapacity < 0) // overflow throw new OutOfMemoryError(); return (minCapacity > MAX_ARRAY_SIZE) ? Integer.MAX_VALUE : MAX_ARRAY_SIZE; } /** * Returns the number of elements in this list. * * @return the number of elements in this list */ public int size() { return size; } /** * Returns <tt>true</tt> if this list contains no elements. * * @return <tt>true</tt> if this list contains no elements */ public boolean isEmpty() { return size == 0; } /** * Returns <tt>true</tt> if this list contains the specified element. * More formally, returns <tt>true</tt> if and only if this list contains * at least one element <tt>e</tt> such that * <tt>(o==null ? e==null : o.equals(e))</tt>. * * @param o element whose presence in this list is to be tested * @return <tt>true</tt> if this list contains the specified element */ public boolean contains(Object o) { return indexOf(o) >= 0; } /** * Returns the index of the first occurrence of the specified element * in this list, or -1 if this list does not contain the element. * More formally, returns the lowest index <tt>i</tt> such that * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>, * or -1 if there is no such index. */ public int indexOf(Object o) { if (o == null) { for (int i = 0; i < size; i++) if (elementData[i]==null) return i; } else { for (int i = 0; i < size; i++) if (o.equals(elementData[i])) return i; } return -1; } /** * Returns the index of the last occurrence of the specified element * in this list, or -1 if this list does not contain the element. * More formally, returns the highest index <tt>i</tt> such that * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>, * or -1 if there is no such index. */ public int lastIndexOf(Object o) { if (o == null) { for (int i = size-1; i >= 0; i--) if (elementData[i]==null) return i; } else { for (int i = size-1; i >= 0; i--) if (o.equals(elementData[i])) return i; } return -1; } /** * Returns a shallow copy of this <tt>ArrayList</tt> instance. (The * elements themselves are not copied.) * * @return a clone of this <tt>ArrayList</tt> instance */ public Object clone() { try { ArrayList<?> v = (ArrayList<?>) super.clone(); v.elementData = Arrays.copyOf(elementData, size); v.modCount = 0; return v; } catch (CloneNotSupportedException e) { // this shouldn't happen, since we are Cloneable throw new InternalError(e); } } /** * Returns an array containing all of the elements in this list * in proper sequence (from first to last element). * * The returned array will be "safe" in that no references to it are * maintained by this list. (In other words, this method must allocate * a new array). The caller is thus free to modify the returned array. * * This method acts as bridge between array-based and collection-based * APIs. * * @return an array containing all of the elements in this list in * proper sequence */ public Object[] toArray() { return Arrays.copyOf(elementData, size); } /** * Returns an array containing all of the elements in this list in proper * sequence (from first to last element); the runtime type of the returned * array is that of the specified array. If the list fits in the * specified array, it is returned therein. Otherwise, a new array is * allocated with the runtime type of the specified array and the size of * this list. * * If the list fits in the specified array with room to spare * (i.e., the array has more elements than the list), the element in * the array immediately following the end of the collection is set to * <tt>null</tt>. (This is useful in determining the length of the * list only if the caller knows that the list does not contain * any null elements.) * * @param a the array into which the elements of the list are to * be stored, if it is big enough; otherwise, a new array of the * same runtime type is allocated for this purpose. * @return an array containing the elements of the list * @throws ArrayStoreException if the runtime type of the specified array * is not a supertype of the runtime type of every element in * this list * @throws NullPointerException if the specified array is null */ @SuppressWarnings("unchecked") public <T> T[] toArray(T[] a) { if (a.length < size) // Make a new array of a's runtime type, but my contents: return (T[]) Arrays.copyOf(elementData, size, a.getClass()); System.arraycopy(elementData, 0, a, 0, size); if (a.length > size) a[size] = null; return a; } // Positional Access Operations @SuppressWarnings("unchecked") E elementData(int index) { return (E) elementData[index]; } /** * Returns the element at the specified position in this list. * * @param index index of the element to return * @return the element at the specified position in this list * @throws IndexOutOfBoundsException { @inheritDoc} */ public E get(int index) { rangeCheck(index); return elementData(index); } /** * Replaces the element at the specified position in this list with * the specified element. * * @param index index of the element to replace * @param element element to be stored at the specified position * @return the element previously at the specified position * @throws IndexOutOfBoundsException { @inheritDoc} */ public E set(int index, E element) { rangeCheck(index); E oldValue = elementData(index); elementData[index] = element; return oldValue; } /** * Appends the specified element to the end of this list. * * @param e element to be appended to this list * @return <tt>true</tt> (as specified by { @link Collection#add}) */ public boolean add(E e) { ensureCapacityInternal(size + 1); // Increments modCount!! elementData[size++] = e; return true; } /** * Inserts the specified element at the specified position in this * list. Shifts the element currently at that position (if any) and * any subsequent elements to the right (adds one to their indices). * * @param index index at which the specified element is to be inserted * @param element element to be inserted * @throws IndexOutOfBoundsException { @inheritDoc} */ public void add(int index, E element) { rangeCheckForAdd(index); ensureCapacityInternal(size + 1); // Increments modCount!! System.arraycopy(elementData, index, elementData, index + 1, size - index); elementData[index] = element; size++; } /** * Removes the element at the specified position in this list. * Shifts any subsequent elements to the left (subtracts one from their * indices). * * @param index the index of the element to be removed * @return the element that was removed from the list * @throws IndexOutOfBoundsException { @inheritDoc} */ public E remove(int index) { rangeCheck(index); modCount++; E oldValue = elementData(index); int numMoved = size - index - 1; if (numMoved > 0) System.arraycopy(elementData, index+1, elementData, index, numMoved); elementData[--size] = null; // clear to let GC do its work return oldValue; } /** * Removes the first occurrence of the specified element from this list, * if it is present. If the list does not contain the element, it is * unchanged. More formally, removes the element with the lowest index * <tt>i</tt> such that * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt> * (if such an element exists). Returns <tt>true</tt> if this list * contained the specified element (or equivalently, if this list * changed as a result of the call). * * @param o element to be removed from this list, if present * @return <tt>true</tt> if this list contained the specified element */ public boolean remove(Object o) { if (o == null) { for (int index = 0; index < size; index++) if (elementData[index] == null) { fastRemove(index); return true; } } else { for (int index = 0; index < size; index++) if (o.equals(elementData[index])) { fastRemove(index); return true; } } return false; } /* * Private remove method that skips bounds checking and does not * return the value removed. */ private void fastRemove(int index) { modCount++; int numMoved = size - index - 1; if (numMoved > 0) System.arraycopy(elementData, index+1, elementData, index, numMoved); elementData[--size] = null; // clear to let GC do its work } /** * Removes all of the elements from this list. The list will * be empty after this call returns. */ public void clear() { modCount++; // clear to let GC do its work for (int i = 0; i < size; i++) elementData[i] = null; size = 0; } /** * Appends all of the elements in the specified collection to the end of * this list, in the order that they are returned by the * specified collection's Iterator. The behavior of this operation is * undefined if the specified collection is modified while the operation * is in progress. (This implies that the behavior of this call is * undefined if the specified collection is this list, and this * list is nonempty.) * * @param c collection containing elements to be added to this list * @return <tt>true</tt> if this list changed as a result of the call * @throws NullPointerException if the specified collection is null */ public boolean addAll(Collection<? extends E> c) { Object[] a = c.toArray(); int numNew = a.length; ensureCapacityInternal(size + numNew); // Increments modCount System.arraycopy(a, 0, elementData, size, numNew); size += numNew; return numNew != 0; } /** * Inserts all of the elements in the specified collection into this * list, starting at the specified position. Shifts the element * currently at that position (if any) and any subsequent elements to * the right (increases their indices). The new elements will appear * in the list in the order that they are returned by the * specified collection's iterator. * * @param index index at which to insert the first element from the * specified collection * @param c collection containing elements to be added to this list * @return <tt>true</tt> if this list changed as a result of the call * @throws IndexOutOfBoundsException { @inheritDoc} * @throws NullPointerException if the specified collection is null */ public boolean addAll(int index, Collection<? extends E> c) { rangeCheckForAdd(index); Object[] a = c.toArray(); int numNew = a.length; ensureCapacityInternal(size + numNew); // Increments modCount int numMoved = size - index; if (numMoved > 0) System.arraycopy(elementData, index, elementData, index + numNew, numMoved); System.arraycopy(a, 0, elementData, index, numNew); size += numNew; return numNew != 0; } /** * Removes from this list all of the elements whose index is between * { @code fromIndex}, inclusive, and { @code toIndex}, exclusive. * Shifts any succeeding elements to the left (reduces their index). * This call shortens the list by { @code (toIndex - fromIndex)} elements. * (If { @code toIndex==fromIndex}, this operation has no effect.) * * @throws IndexOutOfBoundsException if { @code fromIndex} or * { @code toIndex} is out of range * ({ @code fromIndex < 0 || * fromIndex >= size() || * toIndex > size() || * toIndex < fromIndex}) */ protected void removeRange(int fromIndex, int toIndex) { modCount++; int numMoved = size - toIndex; System.arraycopy(elementData, toIndex, elementData, fromIndex, numMoved); // clear to let GC do its work int newSize = size - (toIndex-fromIndex); for (int i = newSize; i < size; i++) { elementData[i] = null; } size = newSize; } /** * Checks if the given index is in range. If not, throws an appropriate * runtime exception. This method does *not* check if the index is * negative: It is always used immediately prior to an array access, * which throws an ArrayIndexOutOfBoundsException if index is negative. */ private void rangeCheck(int index) { if (index >= size) throw new IndexOutOfBoundsException(outOfBoundsMsg(index)); } /** * A version of rangeCheck used by add and addAll. */ private void rangeCheckForAdd(int index) { if (index > size || index < 0) throw new IndexOutOfBoundsException(outOfBoundsMsg(index)); } /** * Constructs an IndexOutOfBoundsException detail message. * Of the many possible refactorings of the error handling code, * this "outlining" performs best with both server and client VMs. */ private String outOfBoundsMsg(int index) { return "Index: "+index+", Size: "+size; } /** * Removes from this list all of its elements that are contained in the * specified collection. * * @param c collection containing elements to be removed from this list * @return { @code true} if this list changed as a result of the call * @throws ClassCastException if the class of an element of this list * is incompatible with the specified collection * (<a href="Collection.html#optional-restrictions">optional</a>) * @throws NullPointerException if this list contains a null element and the * specified collection does not permit null elements * (<a href="Collection.html#optional-restrictions">optional</a>), * or if the specified collection is null * @see Collection#contains(Object) */ public boolean removeAll(Collection<?> c) { Objects.requireNonNull(c); return batchRemove(c, false); } /** * Retains only the elements in this list that are contained in the * specified collection. In other words, removes from this list all * of its elements that are not contained in the specified collection. * * @param c collection containing elements to be retained in this list * @return { @code true} if this list changed as a result of the call * @throws ClassCastException if the class of an element of this list * is incompatible with the specified collection * (<a href="Collection.html#optional-restrictions">optional</a>) * @throws NullPointerException if this list contains a null element and the * specified collection does not permit null elements * (<a href="Collection.html#optional-restrictions">optional</a>), * or if the specified collection is null * @see Collection#contains(Object) */ public boolean retainAll(Collection<?> c) { Objects.requireNonNull(c); return batchRemove(c, true); } private boolean batchRemove(Collection<?> c, boolean complement) { final Object[] elementData = this.elementData; int r = 0, w = 0; boolean modified = false; try { for (; r < size; r++) if (c.contains(elementData[r]) == complement) elementData[w++] = elementData[r]; } finally { // Preserve behavioral compatibility with AbstractCollection, // even if c.contains() throws. if (r != size) { System.arraycopy(elementData, r, elementData, w, size - r); w += size - r; } if (w != size) { // clear to let GC do its work for (int i = w; i < size; i++) elementData[i] = null; modCount += size - w; size = w; modified = true; } } return modified; } /** * Save the state of the <tt>ArrayList</tt> instance to a stream (that * is, serialize it). * * @serialData The length of the array backing the <tt>ArrayList</tt> * instance is emitted (int), followed by all of its elements * (each an <tt>Object</tt>) in the proper order. */ private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException{ // Write out element count, and any hidden stuff int expectedModCount = modCount; s.defaultWriteObject(); // Write out size as capacity for behavioural compatibility with clone() s.writeInt(size); // Write out all elements in the proper order. for (int i=0; i<size; i++) { s.writeObject(elementData[i]); } if (modCount != expectedModCount) { throw new ConcurrentModificationException(); } } /** * Reconstitute the <tt>ArrayList</tt> instance from a stream (that is, * deserialize it). */ private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException { elementData = EMPTY_ELEMENTDATA; // Read in size, and any hidden stuff s.defaultReadObject(); // Read in capacity s.readInt(); // ignored if (size > 0) { // be like clone(), allocate array based upon size not capacity int capacity = calculateCapacity(elementData, size); SharedSecrets.getJavaOISAccess().checkArray(s, Object[].class, capacity); ensureCapacityInternal(size); Object[] a = elementData; // Read in all elements in the proper order. for (int i=0; i<size; i++) { a[i] = s.readObject(); } } } /** * Returns a list iterator over the elements in this list (in proper * sequence), starting at the specified position in the list. * The specified index indicates the first element that would be * returned by an initial call to { @link ListIterator#next next}. * An initial call to { @link ListIterator#previous previous} would * return the element with the specified index minus one. * * The returned list iterator is <a href="#fail-fast">fail-fast</a>. * * @throws IndexOutOfBoundsException { @inheritDoc} */ public ListIterator<E> listIterator(int index) { if (index < 0 || index > size) throw new IndexOutOfBoundsException("Index: "+index); return new ListItr(index); } /** * Returns a list iterator over the elements in this list (in proper * sequence). * * The returned list iterator is <a href="#fail-fast">fail-fast</a>. * * @see #listIterator(int) */ public ListIterator<E> listIterator() { return new ListItr(0); } /** * Returns an iterator over the elements in this list in proper sequence. * * The returned iterator is <a href="#fail-fast">fail-fast</a>. * * @return an iterator over the elements in this list in proper sequence */ public Iterator<E> iterator() { return new Itr(); } /** * An optimized version of AbstractList.Itr */ private class Itr implements Iterator<E> { int cursor; // index of next element to return int lastRet = -1; // index of last element returned; -1 if no such int expectedModCount = modCount; Itr() {} public boolean hasNext() { return cursor != size; } @SuppressWarnings("unchecked") public E next() { checkForComodification(); int i = cursor; if (i >= size) throw new NoSuchElementException(); Object[] elementData = ArrayList.this.elementData; if (i >= elementData.length) throw new ConcurrentModificationException(); cursor = i + 1; return (E) elementData[lastRet = i]; } public void remove() { if (lastRet < 0) throw new IllegalStateException(); checkForComodification(); try { ArrayList.this.remove(lastRet); cursor = lastRet; lastRet = -1; expectedModCount = modCount; } catch (IndexOutOfBoundsException ex) { throw new ConcurrentModificationException(); } } @Override @SuppressWarnings("unchecked") public void forEachRemaining(Consumer<? super E> consumer) { Objects.requireNonNull(consumer); final int size = ArrayList.this.size; int i = cursor; if (i >= size) { return; } final Object[] elementData = ArrayList.this.elementData; if (i >= elementData.length) { throw new ConcurrentModificationException(); } while (i != size && modCount == expectedModCount) { consumer.accept((E) elementData[i++]); } // update once at end of iteration to reduce heap write traffic cursor = i; lastRet = i - 1; checkForComodification(); } final void checkForComodification() { if (modCount != expectedModCount) throw new ConcurrentModificationException(); } } /** * An optimized version of AbstractList.ListItr */ private class ListItr extends Itr implements ListIterator<E> { ListItr(int index) { super(); cursor = index; } public boolean hasPrevious() { return cursor != 0; } public int nextIndex() { return cursor; } public int previousIndex() { return cursor - 1; } @SuppressWarnings("unchecked") public E previous() { checkForComodification(); int i = cursor - 1; if (i < 0) throw new NoSuchElementException(); Object[] elementData = ArrayList.this.elementData; if (i >= elementData.length) throw new ConcurrentModificationException(); cursor = i; return (E) elementData[lastRet = i]; } public void set(E e) { if (lastRet < 0) throw new IllegalStateException(); checkForComodification(); try { ArrayList.this.set(lastRet, e); } catch (IndexOutOfBoundsException ex) { throw new ConcurrentModificationException(); } } public void add(E e) { checkForComodification(); try { int i = cursor; ArrayList.this.add(i, e); cursor = i + 1; lastRet = -1; expectedModCount = modCount; } catch (IndexOutOfBoundsException ex) { throw new ConcurrentModificationException(); } } } /** * Returns a view of the portion of this list between the specified * { @code fromIndex}, inclusive, and { @code toIndex}, exclusive. (If * { @code fromIndex} and { @code toIndex} are equal, the returned list is * empty.) The returned list is backed by this list, so non-structural * changes in the returned list are reflected in this list, and vice-versa. * The returned list supports all of the optional list operations. * * This method eliminates the need for explicit range operations (of * the sort that commonly exist for arrays). Any operation that expects * a list can be used as a range operation by passing a subList view * instead of a whole list. For example, the following idiom * removes a range of elements from a list: * <pre> * list.subList(from, to).clear(); * </pre> * Similar idioms may be constructed for { @link #indexOf(Object)} and * { @link #lastIndexOf(Object)}, and all of the algorithms in the * { @link Collections} class can be applied to a subList. * * The semantics of the list returned by this method become undefined if * the backing list (i.e., this list) is structurally modified in * any way other than via the returned list. (Structural modifications are * those that change the size of this list, or otherwise perturb it in such * a fashion that iterations in progress may yield incorrect results.) * * @throws IndexOutOfBoundsException { @inheritDoc} * @throws IllegalArgumentException { @inheritDoc} */ public List<E> subList(int fromIndex, int toIndex) { subListRangeCheck(fromIndex, toIndex, size); return new SubList(this, 0, fromIndex, toIndex); } static void subListRangeCheck(int fromIndex, int toIndex, int size) { if (fromIndex < 0) throw new IndexOutOfBoundsException("fromIndex = " + fromIndex); if (toIndex > size) throw new IndexOutOfBoundsException("toIndex = " + toIndex); if (fromIndex > toIndex) throw new IllegalArgumentException("fromIndex(" + fromIndex + ") > toIndex(" + toIndex + ")"); } private class SubList extends AbstractList<E> implements RandomAccess { private final AbstractList<E> parent; private final int parentOffset; private final int offset; int size; SubList(AbstractList<E> parent, int offset, int fromIndex, int toIndex) { this.parent = parent; this.parentOffset = fromIndex; this.offset = offset + fromIndex; this.size = toIndex - fromIndex; this.modCount = ArrayList.this.modCount; } public E set(int index, E e) { rangeCheck(index); checkForComodification(); E oldValue = ArrayList.this.elementData(offset + index); ArrayList.this.elementData[offset + index] = e; return oldValue; } public E get(int index) { rangeCheck(index); checkForComodification(); return ArrayList.this.elementData(offset + index); } public int size() { checkForComodification(); return this.size; } public void add(int index, E e) { rangeCheckForAdd(index); checkForComodification(); parent.add(parentOffset + index, e); this.modCount = parent.modCount; this.size++; } public E remove(int index) { rangeCheck(index); checkForComodification(); E result = parent.remove(parentOffset + index); this.modCount = parent.modCount; this.size--; return result; } protected void removeRange(int fromIndex, int toIndex) { checkForComodification(); parent.removeRange(parentOffset + fromIndex, parentOffset + toIndex); this.modCount = parent.modCount; this.size -= toIndex - fromIndex; } public boolean addAll(Collection<? extends E> c) { return addAll(this.size, c); } public boolean addAll(int index, Collection<? extends E> c) { rangeCheckForAdd(index); int cSize = c.size(); if (cSize==0) return false; checkForComodification(); parent.addAll(parentOffset + index, c); this.modCount = parent.modCount; this.size += cSize; return true; } public Iterator<E> iterator() { return listIterator(); } public ListIterator<E> listIterator(final int index) { checkForComodification(); rangeCheckForAdd(index); final int offset = this.offset; return new ListIterator<E>() { int cursor = index; int lastRet = -1; int expectedModCount = ArrayList.this.modCount; public boolean hasNext() { return cursor != SubList.this.size; } @SuppressWarnings("unchecked") public E next() { checkForComodification(); int i = cursor; if (i >= SubList.this.size) throw new NoSuchElementException(); Object[] elementData = ArrayList.this.elementData; if (offset + i >= elementData.length) throw new ConcurrentModificationException(); cursor = i + 1; return (E) elementData[offset + (lastRet = i)]; } public boolean hasPrevious() { return cursor != 0; } @SuppressWarnings("unchecked") public E previous() { checkForComodification(); int i = cursor - 1; if (i < 0) throw new NoSuchElementException(); Object[] elementData = ArrayList.this.elementData; if (offset + i >= elementData.length) throw new ConcurrentModificationException(); cursor = i; return (E) elementData[offset + (lastRet = i)]; } @SuppressWarnings("unchecked") public void forEachRemaining(Consumer<? super E> consumer) { Objects.requireNonNull(consumer); final int size = SubList.this.size; int i = cursor; if (i >= size) { return; } final Object[] elementData = ArrayList.this.elementData; if (offset + i >= elementData.length) { throw new ConcurrentModificationException(); } while (i != size && modCount == expectedModCount) { consumer.accept((E) elementData[offset + (i++)]); } // update once at end of iteration to reduce heap write traffic lastRet = cursor = i; checkForComodification(); } public int nextIndex() { return cursor; } public int previousIndex() { return cursor - 1; } public void remove() { if (lastRet < 0) throw new IllegalStateException(); checkForComodification(); try { SubList.this.remove(lastRet); cursor = lastRet; lastRet = -1; expectedModCount = ArrayList.this.modCount; } catch (IndexOutOfBoundsException ex) { throw new ConcurrentModificationException(); } } public void set(E e) { if (lastRet < 0) throw new IllegalStateException(); checkForComodification(); try { ArrayList.this.set(offset + lastRet, e); } catch (IndexOutOfBoundsException ex) { throw new ConcurrentModificationException(); } } public void add(E e) { checkForComodification(); try { int i = cursor; SubList.this.add(i, e); cursor = i + 1; lastRet = -1; expectedModCount = ArrayList.this.modCount; } catch (IndexOutOfBoundsException ex) { throw new ConcurrentModificationException(); } } final void checkForComodification() { if (expectedModCount != ArrayList.this.modCount) throw new ConcurrentModificationException(); } }; } public List<E> subList(int fromIndex, int toIndex) { subListRangeCheck(fromIndex, toIndex, size); return new SubList(this, offset, fromIndex, toIndex); } private void rangeCheck(int index) { if (index < 0 || index >= this.size) throw new IndexOutOfBoundsException(outOfBoundsMsg(index)); } private void rangeCheckForAdd(int index) { if (index < 0 || index > this.size) throw new IndexOutOfBoundsException(outOfBoundsMsg(index)); } private String outOfBoundsMsg(int index) { return "Index: "+index+", Size: "+this.size; } private void checkForComodification() { if (ArrayList.this.modCount != this.modCount) throw new ConcurrentModificationException(); } public Spliterator<E> spliterator() { checkForComodification(); return new ArrayListSpliterator<E>(ArrayList.this, offset, offset + this.size, this.modCount); } } @Override public void forEach(Consumer<? super E> action) { Objects.requireNonNull(action); final int expectedModCount = modCount; @SuppressWarnings("unchecked") final E[] elementData = (E[]) this.elementData; final int size = this.size; for (int i=0; modCount == expectedModCount && i < size; i++) { action.accept(elementData[i]); } if (modCount != expectedModCount) { throw new ConcurrentModificationException(); } } /** * Creates a <a href="Spliterator.html#binding">late-binding</a> * and fail-fast { @link Spliterator} over the elements in this * list. * * The { @code Spliterator} reports { @link Spliterator#SIZED}, * { @link Spliterator#SUBSIZED}, and { @link Spliterator#ORDERED}. * Overriding implementations should document the reporting of additional * characteristic values. * * @return a { @code Spliterator} over the elements in this list * @since 1.8 */ @Override public Spliterator<E> spliterator() { return new ArrayListSpliterator<>(this, 0, -1, 0); } /** Index-based split-by-two, lazily initialized Spliterator */ static final class ArrayListSpliterator<E> implements Spliterator<E> { /* * If ArrayLists were immutable, or structurally immutable (no * adds, removes, etc), we could implement their spliterators * with Arrays.spliterator. Instead we detect as much * interference during traversal as practical without * sacrificing much performance. We rely primarily on * modCounts. These are not guaranteed to detect concurrency * violations, and are sometimes overly conservative about * within-thread interference, but detect enough problems to * be worthwhile in practice. To carry this out, we (1) lazily * initialize fence and expectedModCount until the latest * point that we need to commit to the state we are checking * against; thus improving precision. (This doesn't apply to * SubLists, that create spliterators with current non-lazy * values). (2) We perform only a single * ConcurrentModificationException check at the end of forEach * (the most performance-sensitive method). When using forEach * (as opposed to iterators), we can normally only detect * interference after actions, not before. Further * CME-triggering checks apply to all other possible * violations of assumptions for example null or too-small * elementData array given its size(), that could only have * occurred due to interference. This allows the inner loop * of forEach to run without any further checks, and * simplifies lambda-resolution. While this does entail a * number of checks, note that in the common case of * list.stream().forEach(a), no checks or other computation * occur anywhere other than inside forEach itself. The other * less-often-used methods cannot take advantage of most of * these streamlinings. */ private final ArrayList<E> list; private int index; // current index, modified on advance/split private int fence; // -1 until used; then one past last index private int expectedModCount; // initialized when fence set /** Create new spliterator covering the given range */ ArrayListSpliterator(ArrayList<E> list, int origin, int fence, int expectedModCount) { this.list = list; // OK if null unless traversed this.index = origin; this.fence = fence; this.expectedModCount = expectedModCount; } private int getFence() { // initialize fence to size on first use int hi; // (a specialized variant appears in method forEach) ArrayList<E> lst; if ((hi = fence) < 0) { if ((lst = list) == null) hi = fence = 0; else { expectedModCount = lst.modCount; hi = fence = lst.size; } } return hi; } public ArrayListSpliterator<E> trySplit() { int hi = getFence(), lo = index, mid = (lo + hi) >>> 1; return (lo >= mid) ? null : // divide range in half unless too small new ArrayListSpliterator<E>(list, lo, index = mid, expectedModCount); } public boolean tryAdvance(Consumer<? super E> action) { if (action == null) throw new NullPointerException(); int hi = getFence(), i = index; if (i < hi) { index = i + 1; @SuppressWarnings("unchecked") E e = (E)list.elementData[i]; action.accept(e); if (list.modCount != expectedModCount) throw new ConcurrentModificationException(); return true; } return false; } public void forEachRemaining(Consumer<? super E> action) { int i, hi, mc; // hoist accesses and checks from loop ArrayList<E> lst; Object[] a; if (action == null) throw new NullPointerException(); if ((lst = list) != null && (a = lst.elementData) != null) { if ((hi = fence) < 0) { mc = lst.modCount; hi = lst.size; } else mc = expectedModCount; if ((i = index) >= 0 && (index = hi) <= a.length) { for (; i < hi; ++i) { @SuppressWarnings("unchecked") E e = (E) a[i]; action.accept(e); } if (lst.modCount == mc) return; } } throw new ConcurrentModificationException(); } public long estimateSize() { return (long) (getFence() - index); } public int characteristics() { return Spliterator.ORDERED | Spliterator.SIZED | Spliterator.SUBSIZED; } } @Override public boolean removeIf(Predicate<? super E> filter) { Objects.requireNonNull(filter); // figure out which elements are to be removed // any exception thrown from the filter predicate at this stage // will leave the collection unmodified int removeCount = 0; final BitSet removeSet = new BitSet(size); final int expectedModCount = modCount; final int size = this.size; for (int i=0; modCount == expectedModCount && i < size; i++) { @SuppressWarnings("unchecked") final E element = (E) elementData[i]; if (filter.test(element)) { removeSet.set(i); removeCount++; } } if (modCount != expectedModCount) { throw new ConcurrentModificationException(); } // shift surviving elements left over the spaces left by removed elements final boolean anyToRemove = removeCount > 0; if (anyToRemove) { final int newSize = size - removeCount; for (int i=0, j=0; (i < size) && (j < newSize); i++, j++) { i = removeSet.nextClearBit(i); elementData[j] = elementData[i]; } for (int k=newSize; k < size; k++) { elementData[k] = null; // Let gc do its work } this.size = newSize; if (modCount != expectedModCount) { throw new ConcurrentModificationException(); } modCount++; } return anyToRemove; } @Override @SuppressWarnings("unchecked") public void replaceAll(UnaryOperator<E> operator) { Objects.requireNonNull(operator); final int expectedModCount = modCount; final int size = this.size; for (int i=0; modCount == expectedModCount && i < size; i++) { elementData[i] = operator.apply((E) elementData[i]); } if (modCount != expectedModCount) { throw new ConcurrentModificationException(); } modCount++; } @Override @SuppressWarnings("unchecked") public void sort(Comparator<? super E> c) { final int expectedModCount = modCount; Arrays.sort((E[]) elementData, 0, size, c); if (modCount != expectedModCount) { throw new ConcurrentModificationException(); } modCount++; } }