异常后继续程序

Question

好的，到目前为止我有这个：

import java.util.Random;
import java.util.Scanner;
class TooHighException extends Exception {}

class TooLowException extends Exception {}

class CorrectException extends Exception {}

public class HighLow {     
    public static void main(String[] args) throws TooLowException, TooHighException, CorrectException {

        Random random = new Random();
        Scanner scanner = new Scanner(System.in);
        int number = random.nextInt(100);
        int guess = -1;
        while (guess != number) {
            System.out.print("Enter your guess: ");
            guess = scanner.nextInt();
            if (guess < number) {
                throw new TooLowException();
            } else if (guess > number) {
                throw new TooHighException();
            } else {
                throw new CorrectException();
            }
        }
    }
}

应该发生的是程序选择一个随机数，并提示用户猜测该数字。然后它会说明猜测是否太高、太低或正确。我知道Exceptions 不应该以这种方式使用，但这是要求的。问题是当我抛出Exception 时，它不允许我输入新的猜测。有什么帮助吗？

Answer 1

您正在使用throw 引发异常，但如果您想处理异常，您应该使用try 和catch 块。请参阅此 answer 以了解不使用 try 和 catch 块时会发生什么。

在可能发生异常的地方使用try 块。

在您的代码中，它发生在 if-else if-else 块中。

所以，

while (guess != number) {
    System.out.print("Enter your guess: ");
    guess = scanner.nextInt();
    try {
        if (guess < number) {
            throw new TooLowException();
        } else if (guess > number) {
            throw new TooHighException();
        } else {
            throw new CorrectException();
        }
    } // end the try block
 }

现在您要处理异常而不是冒泡，因此您需要在 try 块之后立即使用 catch 块。

所以，

while (guess != number) {
    System.out.print("Enter your guess: ");
    guess = scanner.nextInt();
    try {
        if (guess < number) {
            throw new TooLowException();
        } else if (guess > number) {
            throw new TooHighException();
        } else {
            throw new CorrectException();
        }
    } catch(Exception e) {
         System.out.println(e);
    }
 }

当您使用您创建的Exceptions 时，最好提及异常是什么，就像引发异常时的原因一样。

为此，请覆盖 Exception 类的 toString()。如果您在代码中多次使用自定义异常类，则不必每次都在 catch 块中向用户写入消息。

---

编辑：

import java.util.Random;
import java.util.Scanner;
class TooHighException extends Exception {
}
class TooLowException extends Exception {
}
class CorrectException extends Exception {
}
public class HighLow {
     /**
     * @param args the command line arguments
     * @throws TooLowException
     * @throws TooHighException
     * @throws CorrectException
     */
    public static void main(String[] args) {
        Random random = new Random();
        Scanner scanner = new Scanner(System.in);
        int number = random.nextInt(100);
        int guess = -1;
        while (guess != number) {
            System.out.print("Enter your guess: ");
            guess = scanner.nextInt();
            try {
                if (guess < number) {
                    throw new TooLowException();
                } else if (guess > number) {
                    throw new TooHighException();
                } else {
                    throw new CorrectException();
                }
            } catch(Exception e) {
            System.out.println(e);
            }
        }
    } // end main
} // end class

Answer 2

你最好检查一下 try/catch。

while(guess!=number){
try{
        System.out.print("Enter your guess: ");
           guess = scanner.nextInt();
           if (guess < number) {
               throw new TooLowException();
           } else if (guess > number) {
               throw new TooHighException();
           } else {
               throw new CorrectException();
           }
    }



   catch(TooLowException ex){
System.out.println("Too low.");   
}
catch(TooHighException ex){
System.out.println("Too high.");   
}
catch(CorrectException ex){
System.out.println("Correct.");   
}
   finally{
       //This block always executes.
   }
}

Answer 3

您应该考虑使用 try catch 块，而不是仅仅抛出异常。

try { 
    //This block throws the exception.
}
Catch(Exception e) {
      //This block will run next.
}    

Answer 4

像这样？

try {
    if (guess < number) {
        throw new TooLowException(); 
    } else if (guess > number) {
        throw new TooHighException(); 
    } else { 
        throw new CorrectException(); 
    }
} catch (Exception e) {
    e.printStackTrace();
    continue;
}  

Answer 5

while (guess != number) {
    System.out.print("Enter your guess: ");
    guess = scanner.nextInt();
 try{ 
  if (guess < number) {
        throw new TooLowException();// when this line executes exception is thrown, anything written below this line will not run. If there is a catch block to catch this exception below try block, that will run next
    } else if (guess > number) {
        throw new TooHighException();
    } else {
        throw new CorrectException();
    }
 }
 catch(TooLowException e){
    //this will catch the exception you throw.
    //Usually we write e.printStacktrace() to get to know where the error occurred 
   // we also deallocate the allocated resources.
   //but in your case
   System.out.println("Too low");

 }
  catch(TooHighException e){

   System.out.println("Too high");

 }
  catch(CorrectException e){

   System.out.println("Correct");

 }
}

Answer 6

基本上你有以下问题。

异常会终止程序执行，除非它们被 try catch 捕获（请参阅其他答案）。 因此，要继续，您需要捕获异常并打印一些内容以通知用户结果。 但是，如果您这样做，您可以简单地忽略异常并首先打印结果。