Declaring boolean variable

Question

I just saw a code from another developer.

private static boolean _menuNeedsUpdate = false;
private static Boolean _userIsLoggingIn = Boolean.valueOf(false);

I want to know the differences between these two declarations. Can any one please clarify this?

One is a Java "primitive type" (boolean), the other is a Java "class" (Boolean). You can read more about "Wrapper classes" (such as "Boolean") here: https://en.wikipedia.org/wiki/Primitive_wrapper_class — paulsm4, Aug 19 '15 at 08:40
The main practical difference is that `Boolean` can be set to null when `boolean` can not. — Alex Salauyou, Aug 19 '15 at 08:42
@SashaSalauyou `I want to know the differences between these two declarations.` — Suresh Atta, Aug 19 '15 at 08:44
@sᴜʀᴇsʜᴀᴛᴛᴀ I believe the intention is to discover why developer declared first variable as primitive and second as wrapper. — Alex Salauyou, Aug 19 '15 at 08:45
@sᴜʀᴇsʜᴀᴛᴛᴀ nevertheless, since those variables are not `final` it's probably a useful information for the OP to be aware of the possible `null` state of the non-primitive `Boolean`. — Carsten, Aug 19 '15 at 08:46
@Carsten null in `Boolean` can be used in meaning "undefined", which is sometimes very useful. — Alex Salauyou, Aug 19 '15 at 08:49

Suresh Atta · Accepted Answer · 2015-08-19T08:51:05.383

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The first one is a primitive boolean with default value false.

The second one is a Wrapper class of Boolean with default value false.

Apart, I can't see any more difference.

Edit : (Thankyou @carsten @sasha)

Apart from the declaration, another point worth mentioning is with the second declaration the value of _userIsLoggingIn may become null later on where as the primitive cannot.

edited Aug 19 '15 at 08:51

answered Aug 19 '15 at 08:39

Suresh Atta

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Thank you. I thought there is some memory consumption related differences. – user4583559 Aug 19 '15 at 08:57

score 2 · Answer 2 · answered Aug 19 '15 at 08:40

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yes you can use Boolean/boolean instead.

First one is Object and second one is primitive type

On first one, you will get more methods which will be useful

Second one is cheap considering memory expense.

Now choose your way

answered Aug 19 '15 at 08:40

Ahmed Gamal

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score 2 · Answer 3 · answered Aug 19 '15 at 08:49

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Frist one is java primitive and second one is an object/refrence types that wraps a boolean.

Converting between primitives and objects like this is known as boxing/unboxing.

boolean can be yes or no.
Boolean can be yes, no or NULL.

answered Aug 19 '15 at 08:49

Sundeep Badhotiya

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score 0 · Answer 4 · edited May 23 '17 at 11:45

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boolean is a literal true or false, while Boolean is an object wrapper for a boolean.

There is seldom a reason to use a Boolean over a boolean except in cases when an object reference is required, such as in a List.

Boolean also contains the static method parseBoolean(String s), which you may be aware of already.

More info : What's the difference between boolean and Boolean in Java?

edited May 23 '17 at 11:45

Community

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answered Aug 19 '15 at 08:56

Jaydeep Patel

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score 0 · Answer 5 · answered Aug 19 '15 at 08:57

As others said, the first declaration is a primitive while the second is wrapper class.

I would like to add that the second declaration creates a warning when using Java 5 or newer. Declaring _userIsLoggingIn like

private static Boolean _userIsLoggingIn = false;

instead of

private static Boolean _userIsLoggingIn = Boolean.valueOf(false);

will use Boolean.FALSE, avoiding the creation of a new Boolean instance

Declaring boolean variable

5 Answers5