Why is Throwable.fillInStackTrace() method public? Why would someone use it?

Question

I\'m curious why is method fillInStackTrace of java.lang.Throwable public?

This method replaces original stack trace with that from the pl

Answer 1

Perhaps you want to catch an exception and throw a new one that does not encapsulate your previous exception. getStackTrace from the caught one, and set the stackTrace for the new one.

This would also work when you have a singleton exception, instantiated once like:

private static Exception theException = new MyException();

that is thrown multiple times. This would set the stackTrack to something related to the caught exception without the need to expensively create a new exception every time. I think this is how Scala does its continue and break constructs.

try {
    ....
} catch (OtherException oe) {
    theException.fillStackTrace(oe.getStackTrace());
    theException.setMessage(...); //etc
    throw theException;
}

Using static exceptions can be tricky if it can be thrown multiple times concurrently (i.e. in threads)