求JAVA计算器的源程序

我这有一个～～～～～～

import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Calculator
{

public static void main(String[] args)
{
int first,second;
char operator;
try {
BufferedReader firstin = new BufferedReader ( new InputStreamReader (System.in));
BufferedReader secin = new BufferedReader ( new InputStreamReader (System.in));
BufferedReader oper = new BufferedReader ( new InputStreamReader (System.in));
System.out.print("please enter the first value:");
first=Integer.parseInt(firstin.readLine());
System.out.print("please enter the second value:");
second=Integer.parseInt(secin.readLine());

System.out.print("please enter the operator:");
String temp=oper.readLine();
operator=temp.charAt(0);
new Calculator(first,second,operator);
} catch (Exception e) {
System.out.print("Unwanted i