Java try-finally return design question

Question

In Java, a try { ... } finally { ... } is executed somewhat unintuitively to me. As illustrated in another question, Does finally always execute in Java?, if you have a return statement in the try block, it will be ignored if a finally block is defined. For example, the function

boolean test () {     try {         return true;     }     finally {         return false;     } } 

will always return false. My question: why is this? Is there a particular philosophy behind this design decision made by Java? I appreciate any insight, thank you.

Edit: I'm particularly interested as to 'why' Java thinks it's ok to violate the semantics that I define. If I 'return' in a try block, the method should return right then and there. But the JVM decides to ignore my instruction and return from a subroutine that actually hasn't yet been reached.

Answer 1

Technically speaking, the return in the try block won't be ignored if a finally block is defined, only if that finally block also includes a return.

It's a dubious design decision that was probably a mistake in retrospect (much like references being nullable/mutable by default, and, according to some, checked exceptions). In many ways this behaviour is exactly consistent with the colloquial understanding of what finally means - "no matter what happens beforehand in the try block, always run this code." Hence if you return true from a finally block, the overall effect must always to be to return true, no?

In general, this is seldom a good idiom, and you should use finally blocks liberally for cleaning up/closing resources but rarely if ever return a value from them.

Answer 2

If code in finally block ends abruptly, it changes return value/exception from try block. This is considered to be bad practice, and you should not do that.

Among other places, this is also discussed in Java Puzzlers book.