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Primitive wrapper class in Java
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<h2 id="the-difference-between-wrapper-classes-and-primitive-types">The difference between wrapper classes and primitive types</h2> <p>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.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> </p><p>Therefore, the term <i>Primitive wrapper class</i> 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 <i>Non-Primitive</i>. We cannot say that Wrapper classes themselves are Primitive types. They just wrap the primitive types. </p><p>The Byte, Short, Integer, Long, Float, and Double wrapper classes are all <a href="/facts/Subclass_(computer_science)/a7R1xv8n">subclasses</a> of the <a href="https://docs.oracle.com/en/java/javase/19/docs/api/java.base/java/lang/Number.html">Number</a> class. </p><p>The wrapper classes BigDecimal and BigInteger are not one of the primitive wrapper classes but are immutable.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> <a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> </p> <h2 id="atomic-wrapper-classes">Atomic wrapper classes</h2> <p>With Java 5.0, additional wrapper classes were introduced in the <a href="https://docs.oracle.com/en/java/javase/19/docs/api/java.base/java/util/concurrent/atomic/package-summary.html">java.util.concurrent.atomic</a> package. These classes are mutable and cannot be used as a replacement for the regular wrapper classes. Instead, they provide <a href="/facts/Atomic_operation/u3pnNCvs">atomic operations</a> for addition, increment and assignment. </p><p>The atomic wrapper classes and their corresponding types are: </p> <table><tbody><tr><th>Primitive type</th><th>Wrapper class</th></tr><tr><td>int</td><td><a href="https://docs.oracle.com/en/java/javase/19/docs/api/java.base/java/util/concurrent/atomic/AtomicInteger.html">AtomicInteger</a></td></tr><tr><td>long</td><td><a href="https://docs.oracle.com/en/java/javase/19/docs/api/java.base/java/util/concurrent/atomic/AtomicLong.html">AtomicLong</a></td></tr><tr><td>boolean</td><td><a href="https://docs.oracle.com/en/java/javase/19/docs/api/java.base/java/util/concurrent/atomic/AtomicBoolean.html">AtomicBoolean</a></td></tr><tr><td>V</td><td><a href="https://docs.oracle.com/en/java/javase/19/docs/api/java.base/java/util/concurrent/atomic/AtomicReference.html">AtomicReference<V></a></td></tr></tbody></table> <p>The AtomicInteger and AtomicLong classes are subclasses of the Number class. The AtomicReference class accepts the <a href="/facts/TypeParameter/YQEDWumc">type parameter</a> V that specifies the type of the object <a href="/facts/Reference_(computer_science)/1vm2Bph1">reference</a>. (See "<a href="/facts/Generics_in_Java/j8nFhEKq">Generics in Java</a>" for a description of type parameters in Java). V </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Java_Platform%2c_Standard_Edition/1HMPhdsv">java.lang</a></li> <li><a href="/facts/Java_Platform%2c_Standard_Edition/1HMPhdsv">java.lang.reflect</a></li> <li><a href="/facts/Java_(programming_language)/9ScgFyAL">Java programming language</a></li> <li><a href="/facts/Java_syntax/94FIPWBa">Java syntax</a></li> <li><a href="/facts/Java_compiler/ajRWJnlW">Java compiler</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>S. J. Chapman, Introduction to Java, Prentice Hall, 1999. <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>J. Murach, Murach's Java Programming, 4th Edition, Mike Murach and Associates, Inc., 2011. <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>J. R. Hubbard, Programming with Java, Schaum's Outline Series/McGraw Hill, 1998. <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>J. Murach, Murach's Java Programming, 4th Edition, Mike Murach and Associates, Inc., 2011. <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>J. Murach, Murach's Java Programming, 4th Edition, Mike Murach and Associates, Inc., 2011. <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>David O'Meara (April 2003). "Mutable and Immutable Objects: Which classes are Immutable?". Java Ranch. Retrieved 2012-05-14. The classes java.math.BigInteger and BigDecimal are not immutable either, although maybe they should have been. <a href="http://www.javaranch.com/journal/2003/04/immutable.htm" target="_blank">http://www.javaranch.com/journal/2003/04/immutable.htm</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Oracle. "Java documentation from oracle". Immutable arbitrary-precision integers. <a href="http://docs.oracle.com/javase/7/docs/api/java/math/BigInteger.html" target="_blank">http://docs.oracle.com/javase/7/docs/api/java/math/BigInteger.html</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> </ol>