java Random.nextInt()方法

Posted 2020-09-19 Mr_伍先生

public int nextInt(int n)

该方法的作用是生成一个随机的int值，该值介于[0,n)的区间，也就是0到n之间的随机int值，包含0而不包含n。

 

直接上代码：

package org.xiaowu.random.demo;

import java.util.Random;

import org.junit.Test;

public class RandomDemo {
    
    @Test
    public void Demo(){
        Random rnd = new Random();
        int code = rnd.nextInt(8999) + 1000;
        System.out.println("code:"+code);
    }

    
    @Test
    public void Demo1(){
        Random r = new Random();
        int nextInt = r.nextInt();
        Random r1 = new Random(10);
        int nextInt2 = r1.nextInt();
        System.out.println("nextInt:"+nextInt);
        System.out.println("nextInt2:"+nextInt2);
    }

    
    /**
     * 生成[0,1.0)区间的小数
     * 
     */
    @Test
    public void Demo2(){
        Random r = new Random();
        double d1 = r.nextDouble();
        System.out.println("d1:"+d1);
    }

    
    /**
     * 生成[0,5.0)区间的小数
     * 
     */
    @Test
    public void Demo3(){
        Random r = new Random();
        double d2 = r.nextDouble()* 5;
        System.out.println("d1:"+d2);
    }

    
    /**
     * 生成[1,2.5)区间的小数
     * 
     */
    @Test
    public void Demo4(){
        Random r = new Random();
        double d3 = r.nextDouble() * 1.5 + 1;
        System.out.println("d1:"+d3);
    }

    
    /**
     * 生成任意整数
     * 
     */
    @Test
    public void Demo5(){
        Random r = new Random();
        int n1 = r.nextInt();
        System.out.println("d1:"+n1);
    }

    
    
    /**
     * 生成[0,10)区间的整数
     * 
     */
    @Test
    public void Demo6(){
        Random r = new Random();
        int n2 = r.nextInt(10);
        int n3 = Math.abs(r.nextInt() % 10);
        System.out.println("n2:"+n2);
        System.out.println("n3:"+n3);
    }

    
    
    /**
     * 生成[0,10]区间的整数
     * 
     */
    @Test
    public void Demo7(){
        Random r = new Random();
        int n3 = r.nextInt(11);
        int n4 = Math.abs(r.nextInt() % 11);
        System.out.println("n3:"+n3);
        System.out.println("n4:"+n4);
    }

    
    /**
     * 生成[-3,15)区间的整数
     * 
     */
    @Test
    public void Demo8(){
        Random r = new Random();
        int n4 = r.nextInt(18) - 3;
        int n5 = Math.abs(r.nextInt() % 18) - 3;
        System.out.println("n4:"+n4);
        System.out.println("n5:"+n5);
    }
    
}