immutable object.
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Posted By:   Murali_Reddy
Posted On:   Tuesday, October 12, 2004 10:10 PM

if i want to make an obj as immutable,need i specify its class as immutable or that perticular obj.how can i achieve this.

Re: immutable object.

Posted By:   Anonymous  
Posted On:   Friday, December 17, 2004 02:05 AM

An object can only be immutable if it does not have any methods that change ("mutate") its state. So you cannot make an object immutable - the writer of the class must decide whether the class should create immutable objects (like String, Integer, ...) or not (like StringBuffer, customary collections, ...).

If the design is perfect - i.e., the class implements an interface; and all client code is written against the interface, then you can add an "immutable wrapper" via the Decorator pattern by simply implementing

  • all non-mutating methods with a call to a mutable delegate;
  • throwing an UnsupportedOperationException on all mutating methods.
See Collections.unmodifiable...() for an example of this design.

Harald M.

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