注意要引入包  .util.regex 

用于匹配字符序列与正则表达式指定模式的类。 

package com.test1;

import java.io.*; import java.util.regex.*;

public class Test2 {

 /**

  * args   */  public static void main(String[] args) {   // TODO Auto-generated method stub

  try {

   System.out.println("请输入第一个数字:");    BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));    String num1 = reader.readLine();    while(!num1.matches("\\d+"))    {    System.out.println("输入的不是数字，请重新输入");    num1 = reader.readLine();    }    System.out.println("请输入第二个数字:");    String num2 = reader.readLine();    while(!Pattern.compile("[0-9]*").matcher(num2).matches())    {    System.out.println("输入的不是数字，请重新输入");    num2 = reader.readLine();    }    int result = Integer.parseInt(num1) * Integer.parseInt(num2);    System.out.println("乘积是："+ result);    } catch (IOException e) {    // TODO Auto-generated catch block    e.printStackTrace();    }  }

}