数据结构-动态数组(java)

package core.array;

/**
 * Copyright (c) 2020 bigdata ALL Rights Reserved
 * Project: learning
 * Package: base.array
 * Version: 1.0
 *
 * @author qingzhi.wu 2020/7/10 9:57
 */
public class MyArrayList<E> {

    private E[] data;
    private int size;

    /**
     * 构造函数,传入数组的容量capacity构造MyArrayList
     *
     * @param capacity
     */
    public MyArrayList(int capacity) {
        data = (E[])new Object[capacity];
        size = 0;
    }

    /**
     * 无参构造方法,默认容量为10
     */
    public MyArrayList() {
        this(10);
    }

    /**
     * 获取数组汇总的元素个数
     *
     * @return
     */
    public int getSize() {
        return size;
    }

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

    public boolean isEmpty() {
        return getSize() == 0;
    }

    public void addFirst(E e) {
        add(0, e);
    }

    public void addLast(E e) {
        add(size, e);
    }

    public void add(int index, E e) {

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

    private void resize(int capacity) {
       E[] arr = (E[])new Object[capacity];

        System.arraycopy(data,0,arr,0,size);
        data = arr;

    }

    void set(int index, E e) {
        if (index < 0 || index >= size)
            throw new IllegalArgumentException("Get failed");
        data[index] = e;
    }

    public boolean contains(E e) {
        for (int i = 0; i < size; i++) {
            if (data[i].equals(e))
                return true;
        }

        return false;
    }

    public int find(E e) {
        for (int i = 0; i < size; i++) {
            if (data[i] == e)
                return i;
        }
        return -1;
    }

    public E remove(int index) {
        if (index < 0 || index >= size)
            throw new IllegalArgumentException("Delete failed");

        E ret = get(index);

        for (int i = index + 1; i < size; i++) {
            data[i - 1] = data[i];
        }
        size--;
        data[size] = null;
        if(size < data.length/2){
            resize(data.length/2);
        }
        return ret;

    }

    public E get(int index) {
        if (index < 0 || index >= size)
            throw new IllegalArgumentException("Get failed");
        return data[index];
    }

    @Override
    public String toString() {
        StringBuilder res = new StringBuilder();
        res.append(String.format("Array:size = %d,capacity = %d\n", size, getCapacity()));
        res.append("[");
        for (int i = 0; i < size; i++) {
            res.append(data[i]);
            if (i != size - 1) {
                res.append(", ");
            }
        }
        res.append("]");
        return res.toString();
    }


    public E removeFirst(){
        return remove(0);
    }

    public E removeLast(){
        return remove(size-1);
    }

    public void removeElement(E e){
        int index = find(e);
        if(index!=-1){
            remove(index);
        }
    }
}