Is setting a boolean to false redundant?

Question

I have read several previously asked questions and answers on this topic [or quite similar], but none of them have really addressed this point-blank. When declaring a new boolean varibale, is it redundant [e.g. unnecessary] to initialize it to false?

boolean selectedZone = false;

versus just declaring

boolean selectedZone;

The other posts I have looked at are Why is Java's default value for Boolean set to true? and Default value of Boolean in java

Answer 1

It is redundant in most cases. The exception is if it's a local variable, in which case it needs to be initialized before being used. Examples:

class Example{
    boolean value1;//valid, initialized to false
    public void doStuff(){
        boolean value2;//valid, but uninitialized
        System.out.println(value1);//prints "false" (assuming value1 hasn't been changed)
        System.out.println(value2);//invalid, because value2 isn't initialized. This line won't compile.

Some documentation on this: https://web.archive.org/web/20140814175549/https://docs.oracle.com/javase/specs/jls/se5.0/html/typesValues.html#96595

Even though variables are initialized, you still might want to explicitly declare their initial values. It can make the code more legible, and lets people reading your code know that it's a conscious decision to set it to that value.

Related

Answer 2

It is redundant, but I find it clearer.

The same goes for :

int var = 0;

vs.

int var;

I didn't make this up :

Default Values

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.

The following chart summarizes the default values for the above data types.
Data Type Default Value (for fields)
byte 0
short 0
int 0
long 0L
float 0.0f
double 0.0d
char '\u0000'
String (or any object) null
boolean false

(Source)

However, as the comments suggest, if it's a local variable, it must be initialized.