手写ArrayList实例

刺骨的言语ヽ痛彻心扉 2023-07-04 14:09 3阅读 0赞

### 效果 ###

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM1Mzg1Njg3_size_16_color_FFFFFF_t_70]

### 代码块： ###

package com.example.javase;
    
    /**
     * @Description: ArrayList demo
     * @author: YZD
     * @Date: 2020-02-11 15:48
     * @Version: 1.0
     */
    public class arrayListDemo<E> {
        /**
         * 特点：
         * 查询效率高(index)
         * 增删效率低(System.arraycopy)
         * 线程不安全
         * <p>
         * 数组扩容
         */
    
        private Object[] elementData;
        private int size = 0;
    
        //默认长度
        private static final int DEAFULT_CAPACITY = 10;
    
        public arrayListDemo() {
            elementData = new Object[DEAFULT_CAPACITY];
        }
    
        public Object[] getElementData() {
            return elementData;
        }
    
        public void setElementData(Object[] elementData) {
            this.elementData = elementData;
        }
    
        public void add(E object) {
            //扩容
            if (size == elementData.length) {
                Object[] newObj = new Object[size + (size >> 1)];
                System.arraycopy(elementData, 0, newObj, 0, elementData.length);
                elementData = newObj;
            }
            elementData[size++] = object;
        }
    
        public Object get(int index) throws Exception {
            check(index);
            return elementData[index];
        }
    
        public void set(E e, int index) throws Exception {
            check(index);
            elementData[index] = e;
        }
    
        public int size() {
            return size;
        }
    
        public boolean isEmpty() {
            return size == 0;
        }
    
    
        public void remove(E e) throws Exception {
            for (int i = 0; i < size; i++) {
                if (e.equals(get(i))) {
                    // 删除
                    remove(i);
                }
            }
        }
    
        public void remove(int index) throws Exception {
            check(index);
            System.arraycopy(elementData, index + 1, elementData, index, elementData.length - index - 1);
            elementData[--size] = null;
        }
    
        @Override
        public String toString() {
            StringBuilder stringBuilder = new StringBuilder();
            stringBuilder.append("[");
            int count = 0;
            for (int i = 0; i < elementData.length; i++) {
                if (elementData[i] != null) {
                    count += elementData[i].toString().length() + 1;
                    stringBuilder.append(elementData[i]).append(",");
                }
            }
            stringBuilder.setCharAt(count, ']');
            return stringBuilder.toString();
        }
    
        private void check(int index) throws Exception {
            if (index < 0 || index > size) {
                throw new Exception("索引不合法");
            }
        }
    
        public static void main(String[] args) throws Exception {
            arrayListDemo list = new arrayListDemo();
            list.add("a");
            list.add("b");
            list.add("c");
            System.out.println(list.toString());
    //        list.set("set", 0);
            System.out.println(list.get(0));
            list.remove(1);
            list.remove("a");
            System.out.println(list.toString());
    
        }
    }

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM1Mzg1Njg3_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20200211191413580.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM1Mzg1Njg3,size_16,color_FFFFFF,t_70