如何使计算器保持循环？

Question

im having problem here i want my program to loop until the user say it to stop. i want the user to know if he or she want it to continue eg (then type "yes") or if it wants it stop eg(then type "stop").

import java.util.Scanner;

public class Calculator2 {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {

        Scanner scan = new Scanner(System.in);
        String userInput ;


       while( true){
        calculator();
        System.out.println("would you like to make another calculation");
        userInput = scan.nextLine();
        if(userInput != "no"){
            calculator();
        }else{
            System.exit(0);
        }

       }

       }






    public static void calculator()
    {


        // TODO code application logic here

        Scanner user = new Scanner(System.in);
        System.out.println("Enter ");

        double value1 = user.nextDouble();
        String op = user.next();
        double value2 = user.nextDouble();

         if (op.equals("+")){
             Addition(value1,value2);

         }if (op.equals("-")){
             Subtraction(value1,value2);

         }if(op.equals("/")){
             Division(value1,value2);

         }if(op.equals("*")){
             Multiplication(value1,value2);

         }if(op.equals("^")){
             Exponent(value1,value2);

         }if(op.equals("log")){
             NaturalLog(value1);
         }else{

         }



    }
    public static void Addition (double value1, double value2){
        double Sum= value1 + value2;
        System.out.println(Sum);
    }
    public static void Subtraction (double value1 , double value2){
        double diff = value1 - value2;
        System.out.println(diff);
    }
    public static void Division(double value1 , double value2){
        double div = value1 / value2;
        System.out.println(div);
    }
    public static void Multiplication(double value1, double value2){
       double mult =  value1 * value2;
        System.out.println(mult);
    }
    public static void Exponent(double value1 , double value2){
        double exp =  Math.pow(value1, value2);
        System.out.println(exp);
    }
    public static void NaturalLog(double value1){
        double logs = Math.log(value1);
        System.out.println(logs);
    }


}

Answer 1

    if(!"no".equals(userInput)){
        calculator();
    }else{
        System.exit(0);
    }

String compare use .equals()

Answer 2

change

if(userInput != "no"){

to

if(!userInput.equals("no")){

Strings must be compared by the .equals() method, because they are objects. The == method will compare their memory location instead of their value.