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);    }    }