Why can I “fake” the stack trace of an exception in Java?

Question

If I run the following test, it fails:

public class CrazyExceptions {
    private Exception exception;

    @Before
    public void setUp(){
        exception =          


        

Answer 1

You wouldn't want throwing an exception to alter the stack track or you couldn't re-throw an exception safely.

public void throwsException() {
    throw new RuntimeException();
}

public void logsException() {
    try {
        throwsException();
    } catch (RuntimeException e) {
        e.printStrackTrace();
        throw e; // doesn't alter the exception.
    }
}

@Test
public void youCanSeeTheCauseOfAnException(){
    try {
        logsException();
    } catch(Exception e) {
        e.printStrackTrace(); // shows you the case of the exception, not where it was last re-thrown.
    }
}