为什么我得到空

Question

有些人可以帮我解决这个问题。当我尝试打印getCorrectAnswer时，它打印出null。我怎么能得到CorrectAnswer打印correctAnswer谢谢。

public class Test1 { 

    private String correctAnswer; 

    public String getCorrectAnswer() { 
     return correctAnswer; 
    } 

    public void setUpCorrectAnswer() { 
     if (1 == 1) { 
      correctAnswer = "a"; 
     } else { 
      correctAnswer = "d"; 
     } 
    } 

    public static void main(String[] args) { 
     Test1 a = new Test1(); 
     System.out.println(" Answer " + a.getCorrectAnswer()); 
    } 
} 

Answer 1

您需要使用您的setUpCorrectAnswer()方法来设置值。

public static void main (String [] args) { 
    Test1 a = new Test1(); 
    a.setUpCorrectAnswer(); // here 
    System.out.println(" Answer " + a.getCorrectAnswer()); 
} 

Answer 2

您没有调用setUpCorrectAnswer（）。

public static void main(String[] args) { 
    Test1 a = new Test1(); 
    a.setUpCorrectAnswer(); 
    System.out.println(" Answer " + a.getCorrectAnswer()); 
}