Question

When I write a new exception type, am I supposed to write only the constructors needed, or implement all constructors exisiting in Throwable (and calling them by super())?

When thinking about it, I would say implement only what is needed (YAGNI – You Ain’t Gonna Need It). If I need another constructor later, I just add it.

Example:

public void MyException extends RuntimeException {
    // I only need this constructor
    public MyException(Throwable cause) {
        super(cause);
    }
}

Answer 1

Only implement what you’ll need and add as you need them. I usually add the one with the String message and the one you have (for wrapping another Exception).