数组基础:

package com.practice.Array;

public class Array {

    private int[] data;
    private int size;

    //构造函数,传入数组的容量capacity构造Array
    public Array(int capacity){
        data = new int[capacity];
        size = 0;
    }

    //无参数的构造函数,默认数组的容量capacity为10
    public Array(){
        this(10);
    }

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

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

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

    //向所有元素后添加一个新的元素
    public void addLast(int e) {

        /*if(size == data.length)
            throw new IllegalArgumentException("AddLast failed.Array is full.");
        data[size] = e;
        size ++;*/
        add(size,e);
    }

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

    //在第index个位置插入一个新元素e
    public void add(int index,int e){

        if(size == data.length)
            throw new IllegalArgumentException("AddLast failed.Array is full.");

        if(index < 0 || index > size)
            throw new IllegalArgumentException("Add failed.Require index >= 0 and index<=size.");

        for(int i = size -1;i >= index ; i--)
            data[i+1] = data[i];

        data[index] = e;

        size ++;
    }

    // 获取index索引位置的元素
    int get(int index){
        if(index < 0 || index >= size )
            throw new IllegalArgumentException("Get failed.Index is illegal.");
        return data[index];
    }

    //修改index索引位置的元素
    void set(int index, int 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();
    }
}