（JAVA）Break命令在執行時不應該執行

Question

我剛開始學習Java，並且我爲什麼在代碼底部執行我的「break」命令時有點遺憾。

import java.util.Scanner; 

public class GradeValues { 

    private static Scanner scanner; 

    public static void main(String[] args) { 
     boolean keepGoing = true; 
     String grade; // initializing variable for grade 

     while(keepGoing = true){ 
      System.out.println("What percentage did you get? "); //Ask User the question 
      scanner = new Scanner(System.in); //starting the scanner 
      grade = scanner.nextLine(); //storing user input of percentage 

      int percentage = Integer.parseInt(grade); //converting string to a int 

      if(percentage >= 80 && percentage <= 100){ 
       System.out.println("Your grade is an A! Awesome job!"); 
      }else if(percentage >= 70 && percentage <= 79){ 
       System.out.println("Your grade is an B! Nice work!"); 
      }else if(percentage >= 60 && percentage <= 69){ 
       System.out.println("Your grade is an C! That's average. =("); 
      }else if(percentage >= 50 && percentage <= 59){ 
       System.out.println("Your grade is an D! Come on man, you can do better."); 
      }else if(percentage < 50){ 
       System.out.println("Your grade is an F! You need to hit the books again and try again."); 
      }else{ 
       System.out.println("I think you type the wrong value."); 
      } 

      System.out.println("Would you like to check another grade?"); //Asking user if they want to do it again 
      Scanner choice = new Scanner(System.in); //Gets user input 
      String answer = choice.nextLine(); // Stores input in variable "answer" 
      if(answer == "yes"){ 
       keepGoing = true; //While loop should keep going 

      }else{ 
       keepGoing = false; //While loop should stop 
       break; //this should stop program 
      } 
     } 
    } 
} 

考慮到keepGoing布爾變量仍然是正確的（如果用戶鍵入「是」），該應用程序仍將停止，因爲else語句的突破。有人可以告訴我爲什麼這樣做，以及如何解決這個問題？

Answer 1

你不能比較兩個字符串用==操作符。

爲了正確比較字符串，您必須使用equals方法。

例如，在你的代碼替換if/else語句：

if("yes".equals(answer)){ 
    keepGoing = true; //While loop should keep going 

}else{ 
    keepGoing = false; //While loop should stop 
    break; //this should stop program 
} 

Answer 2

answer是一個字符串，它是一種對象類型。你應該把它與equals方法相比，不==操作：

if (answer.equals("yes")) { 
    // etc. 

Answer 3

我想，如果它不是那麼錯字你而條件是不正確while(keepGoing = true) ......應該是while(keepGoing == true)或while(keepGoing)。因此，你不需要中斷。和其他答案中的建議一樣，請使用equals來比較字符串。