java数组的实现

import java.util.Arrays;

public class Array<E> {
    private E[] data;
    private int size;

    //构造函数，传入数组的容量capacity的Array
    @SuppressWarnings("unchecked")
    public Array(int capacity){
        data = (E[]) new Object[capacity];
        size = 0;        
    }

    //午参构造函数，默认capacity为10
    public Array(){
        this(10);
    }

    //获取数组中元素个数
    public int getSize(){
        return size;
    }

    //获取数组的容量
    public int getCapacity(){
        return data.length;
    }

    //判断数组是否为空
    public boolean isEmpty(){
        return size == 0;
    }

    //在数组下标为index的位置插入一个元素
    public void add(int index , E e){

        if(index<0||index>size){
            throw new IllegalArgumentException("add failed , required index > 0 and index < size");
        }
        if(size == data.length){
            resize(data.length * 2);
        }
        for(int i=size-1;i>index;i--){
            data[i+1] = data[i];
        }        
        data[index] = e;
        size++;
    }

    //向所有元素后添加一个新元素
    public void addLast(E e){
        add(size , e);
    }

    //向所有元素前添加一个新元素
    public void addFirst(E e){
        add(0 , e);
    }

    //获取index索引位置的元素
    public E get(int index){
        if(index<0||index>=size){
            throw new IllegalArgumentException("get failed , required index > 0 and index < size");
        }

        return data[index];
    }

    //修改索引index位置的元素为e
    public void set(int index, E e){
        if(index<0||index>=size){
            throw new IllegalArgumentException("set failed , required index > 0 and index < size");
        }

        data[index] = e;
    }

    //判断数组中是否含有元素e
    public boolean contains(E e){
        for(int i = 0;i<size;i++){
            if(e.equals(data[i])){
                return true;
            }
        }
        return false;
    }

    //查找数组中是否含有元素e，返回相应元素的下标
    public int find(E e){
        for(int i = 0;i<size;i++){
            if(e.equals(data[i])){
                return i;
            }
        }
        return -1;
    }

    //从数组中删掉相应下标的元素，返回删掉的元素
    public E remove(int index){
        if(index<0||index>=size){
            throw new IllegalArgumentException("remove failed , required index > 0 and index < size");
        }

        E ret = data[index];
        for(int i=index+1;i<size;i++){
            data[i-1] = data[i];
        }
        size--;
        data[size] = null;

        if(size == data.length/4 && data.length/2 != 0){
            resize(data.length/2);
        }
        return ret;
    }

    //从数组中删掉第一个元素，返回删掉的元素
    public E removeFirst(){
        return remove(0);
    }

    //从数组中删掉最后一个元素，返回删掉的元素
    public E removeLast(){
        return remove(size-1);
    }

    //从数组中删掉元素e
    public void removeElement(E e){
        int index = find(e);

        if(index != -1){
            remove(index);
        }
    }

    @Override
    public String toString() {
        return "Array [data=" + Arrays.toString(data) + ", size=" + size +" Capacity="+data.length+ "]";
    }

    //重新设置数组容量
    private void resize(int newCapacity){
        @SuppressWarnings("unchecked")

        E[] newData = (E[]) new Object[newCapacity];
        for(int i=0;i<size; i++){
            newData[i] = data[i];            
        }        
        data = newData;
    }
}

public static void main(String args[]){

        Array<Integer> array = new Array<Integer>(10);

        for(int i =0;i<10;i++){
            array.add(i, i);
        }

        System.out.println(array.toString());
        array.add(10, 11);
        System.out.println(array.toString());
        array.remove(5);
        System.out.println(array.toString());
    }