Default Boolean value in Java [duplicate]

Answer 1

There is no difference, from:

http://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html

It's not always necessary to assign a value when a field is declared. Fields that are declared but not initialized will be set to a reasonable default by the compiler. Generally speaking, this default will be zero or null, depending on the data type. Relying on such default values, however, is generally considered bad programming style.

Answer 2

The default value of boolean data type is false so we can say that there is no difference.

Answer 3

If you didn't initialize it, it will be false. So there is no difference between them.

Answer 4

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

Answer 5

If you declare as a primitive i.e. boolean. The value will be false by default if it's an instance variable (or class variable).

If it's an instance variable Boolean it will be null.

If it's declared within a method you will have to initialize it, or there will be a compiler error.