覆盖Java中未检查的Exception类中的方法

Question

我试图覆盖Java中的NumberFormatException类中的getMessage()方法，这是一个未检查的异常。出于某种原因，我无法控制它。我知道一定是很简单的东西，但我不明白我错过了什么。有人能帮帮我吗?下面是我的代码:

public class NumberFormatSample extends Throwable{
private static void getNumbers(Scanner sc) {
    System.out.println("Enter any two integers between 0-9 : ");
    int a = sc.nextInt();
    int b = sc.nextInt();
    if(a < 0 || a > 9 || b < 0 || b > 9)
        throw new NumberFormatException();
}
@Override
public String getMessage() {
    return "One of the input numbers was not within the specified range!";
}
public static void main(String[] args) {
    try {
        getNumbers(new Scanner(System.in));
    }
    catch(NumberFormatException ex) {
        ex.getMessage();
    }
}

}

Answer 1

您不需要重写任何内容或创建Throwable的任何子类。

call throw new NumberFormatException(message)

Answer 2

编辑(你的评论后)。

您要找的是:

public class NumberFormatSample {
    private static void getNumbers(Scanner sc) {
        System.out.println("Enter any two integers between 0-9 : ");
        int a = sc.nextInt();
        int b = sc.nextInt();
        if(a < 0 || a > 9 || b < 0 || b > 9)
            throw new NumberFormatException("One of the input numbers was not within the specified range!");
    }
    public static void main(String[] args) {
        try {
            getNumbers(new Scanner(System.in));
        }
        catch(NumberFormatException ex) {
            System.err.println(ex.getMessage());
        }
    }
}

Answer 3

正如其他答案所指出的那样，您实际要做的事情根本不需要重写。

然而，如果你真的需要重写NumberFormatException中的方法，你必须:

• extend 为类，不为Throwable，
• 实例化类的实例，而不是NumberFormatException。

例如:

// (Note: this is not a solution - it is an illustration!)
public class MyNumberFormatException extends NumberFormatException {
    private static void getNumbers(Scanner sc) {
        ...
        // Note: instantiate "my" class, not the standard one.  If you new
        // the standard one, you will get the standard 'getMessage()' behaviour.
        throw new MyNumberFormatException();
    }
    @Override
    public String getMessage() {
        return "One of the input numbers was not within the specified range!";
    }
    public static void main(String[] args) {
        try {
            getNumbers(new Scanner(System.in));
        }
        // Note: we can still catch NumberFormatException, because our
        // custom exception is a subclass of NumberFormatException.
        catch (NumberFormatException ex) {
            ex.getMessage();
        }
    }
}

重写不能通过更改现有类来工作。它的工作原理是基于现有类创建一个新类……使用新类