syntax - In Java, should variables be declared at the top of a function, or as they're needed?

Question

I'm cleaning up Java code for someone who starts their functions by declaring all variables up top, and initializing them to null/0/whatever, as opposed to declaring them as they're needed later on.

What are the specific guidelines for this? Are there optimization reasons for one way or the other, or is one way just good practice? Are there any cases where it's acceptable to deviate from whatever the proper way of doing it is?

Answer 1

Declare variables as close to the first spot that you use them as possible. It's not really anything to do with efficiency, but makes your code much more readable. The closer a variable is declared to where it is used, the less scrolling/searching you have to do when reading the code later. Declaring variables closer to the first spot they're used will also naturally narrow their scope.