Scanner、Random、数组记录

Scanner 键盘键入

package com.it.scanner;

import java.util.Scanner;

public class MyScanner {
    public static void main(String[] args) {
        Scanner s = new Scanner(System.in);

        System.out.println("name");
        String sName = s.next();
        System.out.println("name is " + sName);

        System.out.println("age");
        int sInt = s.nextInt();
        System.out.println("age is " + sInt);
    }
}

Random 随机数

package com.it.rdm;

import java.util.Random;

public class Rdm {
    public static void main(String[] args) {
        Random r = new Random();

        for (int i = 0; i < 10; i++) {
            //  0 - 9
            int r1 = r.nextInt(10);
            System.out.println(r1);
        }
        System.out.println("-------------------");

        //  1 - 10
        int r2 = r.nextInt(10) + 1;
        System.out.println(r2);
        System.out.println("-------------------");

        //  3 - 17
        int r3 = r.nextInt(15) + 3;
        System.out.println(r3);
    }
}

注：
Random 中有 implements RandomGenerator 实现的取值两个值之间的方法 nextInt(int origin, int bound)

数组
1.静态数组
完整： 类型[] 变量名 = new 类型[]{值1, 值2,...}
简写： 类型[] 变量名 = {值1, 值2,...}

// 完整写法
double[] d1 = new double[]{1.33, 2.66, 3.99};
// 简写
double[] d2 = {1.33, 2.66, 3.99}

int[] i1 = new int[]{123, 341};
int[] i2 = {2, 3};

String[] s1 = new String[]{"1231", "dfasd"};
String[] s2 = {"diajs", "sadjoij"};

2.动态数组
类型[] 变量名 = new 类型[储存个数]

int[] i1= new int[5];

i1[0] = 1;
i1[1] = 2;
System.out.println(i1[2]);
System.out.println(i1[3]);

动态数组生成后各种类型的默认值

数据类型	变量类型	默认值
基本类型	byte, short, char, int, long	0
基本类型	float, double	0.0
基本类型	boolean	false
引用类型	类, 接口,数组 ,String	null