java中的常用API

1，length; 返回数组长度

2，Arrays.sort();数组排序

3，Arrays.toString(a)一维数组转化为字符串

4，Arrays.sort(b,(x,y)->{return x[0]-y[0];});二维数组排序

5，deepToString(b) 二维数组转化为字符串

6,Arrays.fill(c,-1); 初始化一维数组

代码实现

import java.util.Scanner;
import java.util.Arrays;
public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] a = new int[n+1];
        for(int i=1;i<=n;i++){
            a[i] = sc.nextInt();
        }

        //1,length; 返回数组长度
        System.out.println(a.length);

        //2,Arrays.sort();数组排序
        Arrays.sort(a);
        for(int i=1;i<=n;i++){
            System.out.printf("%d ",a[i]);
        }
        System.out.println();

        //一维数组转化为字符串
        System.out.println(Arrays.toString(a));

        //3,二维数组排序
        int[][] b = {
                {5,2,3,4},
                {9,6,7,8,},
                {1,10,11,12}
        };
        //按照第i个位置的数的大小排序
        Arrays.sort(b,(x,y)->{
            return x[0]-y[0];
        });
        for(int[] h:b){
            for(int x:h){
                System.out.printf("%d ",x);
            }
            System.out.println();
        }

        //二维数组转化为字符串
        System.out.println(Arrays.deepToString(b));

        //4,初始化一维数组
        int [] c = new int[10];
        Arrays.fill(c,-1);
        for(int x:c)
            System.out.printf("%d ",x);
        //5,

    }
}