Boolean vs boolean in Java

Question

There are discussions around Integer vs int in Java  The default value of the former is null while in the latter it s 0  How about Boolean vs boolean    A variable in my application can have 0 1 values  I would like to use boolean Boolean and prefer not to use int  Can I use Boolean boolean instead

User · Answer

You can use the Boolean constants - Boolean TRUE and Boolean FALSE instead of 0 and 1  You can create your variable as of type boolean if primitive is what you are after  This way you won t have to create new Boolean objects

User · Answer

I am a bit extending provided answers  since so far they concentrate on their  own  artificial terminology focusing on programming a particular language instead of taking care of the bigger picture behind the scene of creating the programming languages  in general  i e  when things like type-safety vs  memory considerations make the difference    int is not boolean  Consider       boolean bar   true            System out printf  Bar is  b n   bar       System out printf  Bar is  d n    bar  1 0       int baz   1             System out printf  Baz is  d n   baz       System out printf  Baz is  b n   baz     with output      Bar is true     Bar is 1     Baz is 1     Baz is true   Java code on 3rd line  bar  1 0 illustrates that bar  boolean  cannot be implicitly converted  casted  into an int  I am bringing this up not to illustrate the details of implementation behind JVM  but to point out that in terms of low level considerations  as memory size  one does have to prefer values over type safety  Especially if that type safety is not truly fully used as in boolean types where checks are done in form of      if value  in  0 1  then cast to boolean type  otherwise throw an exception    All just to state that  0 1   lt   -2 31       2 31 -1   Seems like an overkill  right  Type safety is truly important in user defined types  not in implicit casting of primitives  although last are included in the first    Bytes are not types or bits  Note that in memory your variable from range of  0 1  will still occupy at least a byte or a word  xbits depending on the size of the register  unless specially taken care of  e g  packed nicely in memory - 8  boolean  bits into 1 byte - back and forth    By preferring type safety  as in putting wrapping value into a box of a particular type  over extra value packing  e g  using bit shifts or arithmetic   one does effectively chooses writing less code over gaining more memory   On the other hand one can always define a custom user type which will facilitate all the conversion not worth than Boolean    keyword vs  type  Finally  your question is about comparing keyword vs  type  I believe it is important to explain why or how exactly you will get performance by using preferring keywords   marked  as primitive  over types  normal composite user-definable classes using another keyword class  or in other words  boolean foo   true    vs   Boolean foo   true    The first  thing   type  can not be extended  subclassed  and not without a reason  Effectively Java terminology of primitive and  wrapping classes can be simply translated into inline value  a LITERAL or a constant that gets directly substituted by compiler whenever it is possible to infer the substitution or  if not - still fallback into wrapping the value     Optimization is achieved due to trivial       Less runtime casting operations    more speed     That is why when the actual type inference is done it may  still  end up in instantiating of wrapping class with all the type information if necessary  or converting casting into such    So  the difference between boolean and Boolean is exactly in Compilation and Runtime  a bit far going but almost as instanceof vs  getClass       Finally  autoboxing is slower than primitives  Note the fact that Java can do autoboxing is just a  syntactic sugar   It does not speed up anything  just allows you to write less code  That s it  Casting and wrapping into type information container is still performed  For performance reasons choose arithmetics which will always skip extra housekeeping of creating class instances with type information to implement type safety  Lack of type safety is the price you pay to gain performance  For code with boolean-valued expressions type safety  when you write less and hence implicit code  would be critical e g  for if-then-else flow controls

User · Answer

One observation   though this can be thought of side effect   boolean being a primitive can either say yes or no   Boolean is an object  it can refer to either yes or no or  don t know  i e  null

User · Answer

Basically boolean represent a primitive data type where Boolean represent a reference data type  this story is started when Java want to become purely object oriented it s provided wrapper class concept to over come to use of primitive data type   boolean b1  Boolean b2    b1 and b2 are not same

User · Answer

You can use Boolean   boolean  Simplicity is the way to go  If you do not need specific api  Collections  Streams  etc   and you are not foreseeing that you will need them - use primitive version of it  boolean     With primitives you guarantee that you will not pass null values  You will not fall in traps like this  The code below throws NullPointerException  from  Booleans  conditional operators and autoboxing    public static void main String   args  throws Exception       Boolean b   true   returnsNull     false     NPE on this line      System out println b     public static Boolean returnsNull         return null    Use Boolean when you need an object  eg    Stream of Booleans   Optional Collections of Booleans

User · Answer

Boolean is threadsafe  so you can consider this factor as well along with all other listed in answers

User · Answer

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  The second will save you a lot more memory  so go for it   Now choose your way

User · Answer

Boolean wraps the boolean primitive type  In JDK 5 and upwards  Oracle  or Sun before Oracle bought them  introduced autoboxing unboxing  which essentially allows you to do this  boolean result   Boolean TRUE    or  Boolean result   true     Which essentially the compiler does    Boolean result   Boolean valueOf true     So  for your answer  it s YES

[java] Boolean vs boolean in Java

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