2位“随机”数四则运算

今天上课老师现场留了个小作业：产生30个随机数四则运算

遇到了些问题，因为初学JAVA，random的用法一直出错。后来网上查了查。才理解。

Random rand = new Random();

            int firstnum = rand.nextInt(99)+1;可以产生1到99的随机数。如果是从0开始，就是int firstnum = rand.nextInt(100);产生0到99的随机数。

以下是我的具体代码：

package jian;

import java.util.Random;

public class jian {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		for(int i=0;i<30;i++){
			Random rand = new Random();
			int firstnum = rand.nextInt(99)+1;
			int secondnum = rand.nextInt(99)+1;
			int num = rand.nextInt(4)+1;
			if(num==1)
				System.out.println(firstnum+" + "+secondnum+" = ");
			if(num==2)
				System.out.println(firstnum+" - "+secondnum+" = ");
			if(num==3)
				System.out.println(firstnum+" * "+secondnum+" = ");
			if(num==4)
				System.out.println(firstnum+" / "+secondnum+" = ");
		}
	}
}