Page History

Wiki MarkupImmutability helps to supporting security reasoning. It is safe to share immutable objects, without risk that the recipient can modify something that we are relying on \[ [Mettler 2010B|AA. References#Mettler 2010B]\].unmigrated-wiki-markup

Programmers could incorrectly expect that declaring a field or variable {{final}} makes the referenced object immutable. Declaring variables that have a primitive type to be {{final}} does prevent changes to their values after initialization (unless the unsupported {{sun.misc.Unsafe}} class is used). However, when the variable has a reference type, the presence of a {{final}} clause in the declaration only makes _the reference itself_ immutable. The {{final}} clause has no effect on the referenced object. Consequently, the fields of the referenced object can be mutable. For example, according to the _Java Language Specification_ \[ [JLS 2005|AA. References#JLS 05]\], [§4.12.4|http://java.sun.com/docs/books/jls/third_edition/html/typesValues.html#4], §4.12.4], "{{final}} Variables,"

If a final variable holds a reference to an array, then the components of the array may be changed by operations on the array, but the variable will always refer to the same array.

...

Bibliography

...

04. Object Orientation (OBJ)