2随机数

随机数

import java.util.Random;
public class Main {
    public static void main(String[] args) {
        Random r = new Random();
        int data = r.nextInt(10);
        //0-9之间的随机数；不包括10
        int data2 = data + 1;
        //1-10之间的随机数；
        System.out.println(data);
    }
}

数组

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        int[] ages = new int[]{1, 2, 3, 4};
        //简化写法；
        int[] ages2 = {12, 24, 36};
        ages[2] = 1;
        System.out.print(ages[2]);
        int len = ages.length;
        //不需要括号
    }
}