Java - Object declaration out of while loop

Question

Could you explain to me which code is better (more optimal) and why?

Vesion 1:

while(something){
Runnable task = (Runnable) taskQueue.dequeue();
Throwable  ex = null;
...
}

Version 2:

Runnable task;
Throwable ex;

while(something){
task = (Runnable) taskQueue.dequeue();
ex = null;
...
}

For me it looks like second version is optimized because variable declaration is out of while loop.

Answer 1

At the bytecode level, there is no such thing as inner block. All local variables are declared at the scope of the method. As a result, both your variants should produce equivalent bytecode. To make sure, decompile them with javap and look at the bytecode. From the programmer's point of view, version 1 is more clear and concise.

Answer 2

The first code style is more preferred according to concept "minimization of life variables" (R. Martin "Clean code"). In byte-code there is no diff.