Why Wrapper class like Boolean in java is immutable?

Why Wrapper class like Boolean in java is immutable?

References

Reference NO 1

http://stackoverflow.com/questions/15194226/why-wrapper-class-like-boolean-in-java-is-immutable

Reference NO 2

http://stackoverflow.com/questions/1385481/mutable-boolean-field-in-java

Reference NO 3

http://www.roseindia.net/java/wrapper-class/wrapper-classes.shtml

Reference NO 4

http://en.wikipedia.org/wiki/Primitive_wrapper_class

Reference NO 5

http://www.coderanch.com/t/551096/java/java/Time-revisit-primitive-immutable-wrapper

Reference NO 6

http://www.javaranch.com/journal/2003/04/immutable.htm

Reference NO 7

http://www.itcsolutions.eu/2011/04/22/tutorial-java-scjp-15-wrapper-classes-for-primitive-types/

Reference NO 8

http://java-questions.com/ImmutableClass-interview-questions.html