Java如果语句导致方法执行两次

Question

我想做一个测验类型的游戏，并且由于某种原因，当我在它下面添加if语句时，会执行两次ask方法。在它返回之前，你会问这个问题两次，不管它是否正确。

，询问问题

import java.util.Scanner; 

public class QuizGame 
{ 
private int correct; 
private int wrong; 
private Scanner inputScan; 
private Quiz customQuiz; 

public QuizGame() 
{ 
    correct=0; 
    wrong=0; 
    inputScan = new Scanner(System.in); 
} 

private void startQuiz() 
{ 
     System.out.println("Use custom upper limit? (y/n) "); 
     String custom = inputScan.next(); 

     if(custom.equalsIgnoreCase("y")) 
     { 
      System.out.println("What do you want to be your upper limit?"); 
      int limit = inputScan.nextInt(); 
      customQuiz = new Quiz(limit); 
      customQuiz.ask(); 

      if(customQuiz.ask()) 
      { 
       correct +=1; 
       System.out.println("Correct!"); 
      } 
      else 
      { 
       wrong+=1; 
       System.out.println("Wrong!"); 
      } 
     } 
    } 

    public static void main(String[] args) 
    { 
     QuizGame quiz1 = new QuizGame(); 
     quiz1.startQuiz(); 
    } 
} 

其他类：

import java.util.Random; 
import java.util.Scanner; 

public class Quiz 
{ 
    private Random rGen; 
    private int num1; 
    private int num2; 
    private Scanner getInput; 
    private int answer; 

    public Quiz(int n1) 
    { 
     rGen = new Random(); 
     num1 = rGen.nextInt(n1); 
     num2 = rGen.nextInt(n1); 
     getInput = new Scanner(System.in); 

    } 

    public boolean ask() 
    { 
     int answer = num1 * num2; 
     System.out.println("What is " + num1 + " x " + num2); 
     int userAnswer = getInput.nextInt(); 

     return answer == userAnswer; 
    } 
} 

我孤立的问题，它肯定似乎是if语句：if(customGame.ask()) {}在驱动程序类，但我不明白为什么。这不像if(customGame.ask())再次调用ask方法，它只是测试它是否返回true？我也尝试过，只是if(customGame.ask() == true)仍然没有。

Answer 1

好了，你在呼唤customQuiz.ask()两次：

customQuiz.ask(); 

if (customQuiz.ask()) 
{ 
    correct += 1; 
    System.out.println ("Correct!"); 
} 

简单地调用它只是一次：

if (customQuiz.ask()) 
{ 
    correct +=1; 
    System.out.println ("Correct!"); 
} 

或（由@RobertHarvey所建议的），你可以把一个方法的结果变量并在以后使用它：

boolean correct = customQuiz.ask(); 
if (correct) 
{ 
    correct += 1; 
    System.out.println ("Correct!"); 
}