immutable

[chalapathi]

How to create immutable class without using final keyword?

[GabrielNegut]

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).

[copeg]

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:

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.