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Thread: immutable

  1. #1
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    Default immutable

    How to create immutable class without using final keyword?


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    Default Re: immutable

    final does not mean the class is immutable, you just can't reassign the variable to another object instance.

    Example:

    final MyObject obj = new MyObject();
     
    // obj = new MyObject();
    // you can't reassign it
     
    obj.setField(true);
    // but you can modify it

    If you want to create an immutable class, don't make any public mutators (methods which modify the object's fields).
    Last edited by GabrielNegut; May 7th, 2012 at 08:13 AM.

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    Default Re: immutable

    Quote Originally Posted by GabrielNegut View Post
    final does not mean the class is immutable, you just can't reassign the variable to another object instance.
    Final means different things in difference contexts See Writing Final Classes and Methods (The Java™ Tutorials > Learning the Java Language > Interfaces and Inheritance)
    To quote:
    Quote Originally Posted by Oracle
    A class that is declared final cannot be subclassed. This is particularly useful, for example, when creating an immutable class like the String class
    Marking a class as final does not by default mean the class is immutable. Encapsulating fields and not providing setters is a step in the right direction, but depending upon what the fields are, one may also need to have some way to deep copy fields which can potentially be modified by clients when accessed by getters.

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