Default Boolean value in Java [duplicate]

Question

I just want to know if there is a difference in Java between:

private boolean someValue;

private boolean someValue = false;

The second line maybe is just a time wasting?

EDIT (SUMMARY):

From the answers I found that there is almost no difference, but:

"Relying on such default values, however, is generally considered bad programming style."

But there are some strong arguments not to do so - see accepted answer below.

EDIT 2

I found that in some cases boolean value must be initialized, otherwise the code will not compile:

boolean someValue;
if (someValue) { // Error here
     // Do something
}

In my NetBeans IDE I got the error - "variable someValue might not have been initialized".

It's getting interesting.. :)

Answer 1

All instance and class variables in Java are initialised with a default value:

For type boolean, the default value is false.

So your two statements are functionally equivalent in a single-threaded application.

Note however that boolean b = false; will lead to two write operations: b will first be assigned its default value false then it will be assigned its initial value (which happens to be false as well). This may have an importance in a multi-threaded context. See this example of how explicitly setting the default value can introduce a data race.

Relying on such default values, however, is generally considered bad programming style.

I would argue the opposite: explicitly setting default values is bad practice:

• it introduces unnecessary clutter
• it may introduce subtle concurrency issues