java Random.nextInt()方法

  1 package org.xiaowu.random.demo;
  2 
  3 import java.util.Random;
  4 
  5 import org.junit.Test;
  6 
  7 public class RandomDemo {
  8     
  9     @Test
 10     public void Demo(){
 11         Random rnd = new Random();
 12         int code = rnd.nextInt(8999) + 1000;
 13         System.out.println("code:"+code);
 14     }
 15 
 16     
 17     @Test
 18     public void Demo1(){
 19         Random r = new Random();
 20         int nextInt = r.nextInt();
 21         Random r1 = new Random(10);
 22         int nextInt2 = r1.nextInt();
 23         System.out.println("nextInt:"+nextInt);
 24         System.out.println("nextInt2:"+nextInt2);
 25     }
 26 
 27     
 28     /**
 29      * 生成[0,1.0)区间的小数
 30      * 
 31      */
 32     @Test
 33     public void Demo2(){
 34         Random r = new Random();
 35         double d1 = r.nextDouble();
 36         System.out.println("d1:"+d1);
 37     }
 38 
 39     
 40     /**
 41      * 生成[0,5.0)区间的小数
 42      * 
 43      */
 44     @Test
 45     public void Demo3(){
 46         Random r = new Random();
 47         double d2 = r.nextDouble()* 5;
 48         System.out.println("d1:"+d2);
 49     }
 50 
 51     
 52     /**
 53      * 生成[1,2.5)区间的小数
 54      * 
 55      */
 56     @Test
 57     public void Demo4(){
 58         Random r = new Random();
 59         double d3 = r.nextDouble() * 1.5 + 1;
 60         System.out.println("d1:"+d3);
 61     }
 62 
 63     
 64     /**
 65      * 生成任意整数
 66      * 
 67      */
 68     @Test
 69     public void Demo5(){
 70         Random r = new Random();
 71         int n1 = r.nextInt();
 72         System.out.println("d1:"+n1);
 73     }
 74 
 75     
 76     
 77     /**
 78      * 生成[0,10)区间的整数
 79      * 
 80      */
 81     @Test
 82     public void Demo6(){
 83         Random r = new Random();
 84         int n2 = r.nextInt(10);
 85         int n3 = Math.abs(r.nextInt() % 10);
 86         System.out.println("n2:"+n2);
 87         System.out.println("n3:"+n3);
 88     }
 89 
 90     
 91     
 92     /**
 93      * 生成[0,10]区间的整数
 94      * 
 95      */
 96     @Test
 97     public void Demo7(){
 98         Random r = new Random();
 99         int n3 = r.nextInt(11);
100         int n4 = Math.abs(r.nextInt() % 11);
101         System.out.println("n3:"+n3);
102         System.out.println("n4:"+n4);
103     }
104 
105     
106     /**
107      * 生成[-3,15)区间的整数
108      * 
109      */
110     @Test
111     public void Demo8(){
112         Random r = new Random();
113         int n4 = r.nextInt(18) - 3;
114         int n5 = Math.abs(r.nextInt() % 18) - 3;
115         System.out.println("n4:"+n4);
116         System.out.println("n5:"+n5);
117     }
118     
119 }