一、数组的扩容

package com.jun.demo01;

import java.util.Scanner;

public class demo12 {
    public static void main(String[] args) {
        int[] arr1 = {1, 2, 3};

        //创建一个用户输入
        Scanner scanner = new Scanner(System.in);
        do {
            int[] arr2 = new int[arr1.length + 1];
            System.out.println("请输入你要添加的元素");
            int scn = scanner.nextInt();
            for (int i = 0; i < arr1.length; i++) {
                arr2[i] = arr1[i];
            }
            arr2[arr2.length - 1] = scn;
            arr1 = arr2;
            //判断用户是否继续输入
            System.out.println("是否继续添加元素");
            char c = scanner.next().charAt(0);

            if (c == 'y') {
                break;
            }
        } while (true);
        //遍历数组
        for (int i = 0; i < arr1.length; i++) {
            System.out.print(arr1[i]);
        }
    }
}

?二、数组缩减

package com.jun.demo01;

import java.util.Scanner;

public class demo13 {
    public static void main(String[] args) {
        int[] arr = {1, 2, 3, 4,5};

        Scanner sc = new Scanner(System.in);
        do{
            int[] arrNew = new int[arr.length - 1];
            for(int i = 0; i < arrNew.length; i++){
                arrNew[i] = arr[i];

            }
            arr = arrNew;
            if(arr.length < 2){
                System.out.println("数组元素个数为1，不能删除");
                break;
            }

            System.out.print("数组的元素个数为"+arrNew.length+"是否继续删除： ");
            char c1 = sc.next().charAt(0);
            if (c1 == 'n'){
                break;
            }
        } while(true);
    }
}