使我自己成为Java的例外

Question

I try to make my own exceptions in Java.

I have a parent class like :

public class PException extends Exception {
    public PException(String msg) {
         super(msg);
    }
}

and two children classes like :

public class noGoalException extends PException {
    public noGoalException(){
        super("No Goal");
    }
}

I call it like that :

in the main :

try {
    Starter s = new Starter("res/init");
} catch (PException e) {
    e.getMessage();
}

and in my method :

 private void parseGoals() throws PException {
     [...]
     if (i == 0) {
        throw new noGoalException();
     }
}

and Starter :

public Starter(String fileName) throws GPException {
    [...]
    parseGoals();
}

I specify that i=0 for the tests.

The probleme is that my exception in never throws. Is there something wrong ?

Thanks for helping me.

Answer 1

Like @Berger also mensions in a comment: instead of e.getMessage() do either:

try {
    Starter s = new Starter("res/init");
} catch (PException e) {
    System.out.println(e.getMessage());
}

or

try {
    Starter s = new Starter("res/init");
} catch (PException e) {
    e.printStackTrace();
}

If that still not prints anything please provide more code where your i comes from so we can check why the error is not thrown.

Answer 2

This here is not correct and is the reason why you see nothing when the exception is thrown

try {
    Starter s = new Starter("res/init");
} catch (PException e) {
    e.getMessage();
}

e.getMessage() returns a String and that is just getting lost in the stack

Do instead:

System.out.println(e.getMessage());

in the catch

or just call e.printStackTrace()