用户提示使用if语句

Question

我试图编写一个程序，询问用户是否怀孕。我遇到的问题是，如果用户输入“可能”或任何其他回答，而不是“是”或“否”，我希望程序说“是或不是”，然后提示用户再次回答问题。相反，它会打印出“这是一个是或否的问题”和“你怀孕了吗？”但它不能接受另一个回应。这是我想要做的正确格式吗？换句话说，我希望我的程序不断询问用户是否怀孕，直到我得到是或否的答案。

import acm.program.*; 

public class AskProgram extends ConsoleProgram{ 
    public void run(){ 

     String answer = readLine(" are you pregnant? "); 

     if (answer.equals("yes")) { 
      println("Great! Congratulations "); 
     } else if (answer.equals("no")) { 
      println("keep trying it will happen."); 
     } else { 
      println("Its a yes or no question"); 
      readline("are you pregnant? "); 
     }   
    } 
} 

Answer 1

这将重复块，直到用户输入或者“是”或“否”：

String answer = ""; 
while (!answer.equalsIgnoreCase("yes") && !answer.equalsIgnoreCase("no")) { 
    answer = readLine("Are you pregnant?"); 
    if (answer.equalsIgnoreCase("yes")) { 
     println("Great! Congratulations "); 
     break; 
    } else if (answer.equalsIgnoreCase("no")) { 
     println("keep trying it will happen."); 
     break; 
    } else { 
     println("Its a yes or no question"); 
     readline("are you pregnant? "); 
    }  
} 

Answer 2

这是使用递归版本（和返回值）：

private static boolean isPregnant() { 
    String answer = readLine("Are you pregnant?"); 
    if (answer.equalsIgnoreCase("yes")) { 
     println("Great! Congratulations "); 
     return true; 
    } else if (answer.equalsIgnoreCase("no")) { 
     println("keep trying it will happen."); 
     return false; 
    } else { 
     println("It's a yes or no question"); 
     return isPregnant(); 
    } 

}