自定义Java动态数组

比眉伴天荒 2022-01-13 12:41 225阅读 0赞

**前言:**  
基于Java提供的静态数组,自定义实现的动态数组  
代码如下:

/**
     * @ClassName Array
     * @Description  基于java数组进行二次封装
     * @Author lilei
     * @Date 16/06/2019 11:09
     * @Version 1.0
     **/
    
    public class Array<E> {
    
        private E[] data;
        private int size;
    
        public Array(int capacity){
            data = (E[]) new Object[capacity];
            size = 0;
        }
    
        public Array(){
            this(10);
        }
    
        public int getCapacity() {
            return data.length;
        }
    
    
        public int getSize() {
            return size;
        }
    
        // 判断是否为空
        public boolean isEmpty(){
            return size == 0;
        }
    
        // 增加一个元素
        public void addLast(E e){
            if (size == data.length)
                resize(2 * data.length);
            data[size++] = e;
        }
    
        //指定索引增加元素
        public void add(int index, E e){
            if (index < 0 || index > size){
                throw new IllegalArgumentException("Add failed. Require index >= 0 and index < size.");
            }
    
            if (size == data.length){
                resize(2 * data.length);
            }
    
            if (size == data.length/2)
                resize(data.length/2);
    
            for (int i = size -1; i >= index ; i--) {
                data[i + 1] = data[i];
            }
            data[index] = e;
            size++;
        }
    
        private void resize(int newCapacity) {
            E[] newData = (E[])new Object[newCapacity];
            for (int i = 0; i < size; i++) {
                newData[i] = data[i];
            }
            data = newData;
        }
    
        // 在数组开头增加元素
        public void addFirst(E e){
            add(0, e);
        }
    
        // 获得指定索引元素
        public E get(int index){
            if (index < 0 || index >= size)
                throw new IllegalArgumentException("Get failed. Index is illegal");
            return data[index];
        }
    
        // 查找数组中是否有元素e
        public boolean contains(E e){
            for (int i = 0; i < size; i++) {
                if (data[i].equals(e))
                    return true;
            }
            return false;
        }
    
        // 查找元素e所在索引
        public int find(E e){
            for (int i = 0; i < size; i++) {
                if (data[i].equals(e))
                    return i;
            }
            return -1;
        }
    
        // 从数组中删除index位置的元素, 返回删除的元素
        public E remove(int index){
            if (index < 0 || index >= size)
                throw new IllegalArgumentException("Set failed. Index is illegal");
            E ret = data[index];
            for (int i = index +1 ; i < size ; i++)
                data[i-1] = data[i];
            size--;
            data[size] = null; // loitering objects != memory leak
            return ret;
        }
    
        // 从数组中删除第一个元素, 返回删除的元素
        public E removeFirst(){
            return remove(0);
        }
    
        // 从数组中删除最后一个元素
        public E removeLast(){
            return remove(size-1);
        }
    
        // 删除指定元素
        public void removeElement(E e){
            int index = find(e);
            if (index != -1)
                remove(index);
        }
    
        // 修改指定索引元素
        public void set(int index, E e){
            if (index < 0 || index >= size)
                throw new IllegalArgumentException("Set failed. Index is illegal");
            data[index] = e;
        }
    
        @Override
        public String toString(){
            StringBuilder res = new StringBuilder();
            res.append(String.format("Array: size = %d, capacity = %d\n", size, data.length));
            res.append('[');
            for (int i = 0; i < size; i++) {
                res.append(data[i]);
                if (i != size -1)
                    res.append(", ");
            }
            res.append(']');
            return res.toString();
        }
    
    }