Primitive wrapper class in Java: Difference between revisions

Revision as of 10:26, 13 December 2017

Revision as of 10:26, 27 December 2017

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In object oriented programming, a '''wrapper class''' is a class that [[Encapsulation (computer programming)|encapsulates]] types, so that those types can be used to create object instances and methods in another class that need those types. So a '''primitive wrapper class''' is a wrapper class that encapsulates, hides or ''wraps'' data types from the eight primitive data types,<ref>S. J., Chapman, ''Introduction to Java'', Prentice Hall, 1999.</ref> so that these can be used to create instantiated objects with methods in another class or in other classes.<ref name=murach>J. Murach, ''Murach's Java Programming'', 4th Edition, Mike Murach and Associates, Inc., 2011.</ref><ref>J. R., Hubbard, ''Programming with Java'', Schaum's Outline Series/McGraw Hill, 1998.</ref> The primitive wrapper classes are found in the Java API.

Primitive wrapper classes are used to create an {{Javadoc:SE|java/lang|Object}} that needs to represent primitive types in {{Javadoc:SE|java/util|Collection}} classes (i.e., in the Java API), in the {{Javadoc:SE|package=java.util|java/util}} package and in the {{Javadoc:SE|package=java.lang.reflect|java/lang/reflect}} [[Reflection (computer science)|reflection]] package. Collection classes are Java API -defined classes that can store objects in a manner similar to how data structures like arrays store primitive data types like, '''int''', '''double''', '''long''' or '''char''', etc.,<ref>J. Murach, ''Murach's Java Programming'', 4th Edition, Mike Murach and Associates, Inc., 2011.<name=murach/ref> Butbut arrays store primitive data types while collections actually store objects.

The primitive wrapper classes and their corresponding primitive types are:

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==The difference between wrapper classes and primitive types==

Primitive wrapper classes are not the same thing as primitive types. Whereas variables, for example, can be declared in Java as data types '''double''', '''short''', '''int''', etc., the primitive wrapper classes create instantiated objects and methods that inherit but hide the primitive data types, not like variables that are assigned the data type values.<ref>J. Murach, ''Murach's Java Programming'', 4th Edition, Mike Murach and Associates, Inc., 2011.<name=murach/ref>

Therefore, the term ''Primitive wrapper class'' does not mean that wrapper classes are primitive types. It should be understood to be a class that wraps primitive types. Wrapper classes can be used to store the same value as of a primitive type variable but the instances/objects of wrapper classes themselves are ''Non-Primitive''. We cannot say that Wrapper classes themselves are Primitive types. They just wrap the primitive types.

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| title = Mutable and Immutable Objects: Which classes are Immutable?

| author = David O'Meara

| date = April 2003-04

| publisher = Java Ranch

| accessdate = 2012-05-14