how do I make a class immutable?

[sanjeev katthi]

Hi.. i am new to this forum... i have a doubt.. please answer me immediately..

my question is how can i make a class immutable...??
[ June 12, 2007: Message edited by: Bear Bibeault ]

[Rahul Bhattacharjee]

public class Test {
 
private String name;
 
public Test(String name){
this.name = name;
}
 
public String getName(){
 return name;
}
}

[arulk pillai]

Writing an immutable class is generally easy but there can be some tricky situations. Follow the following guidelines:

1.A class is declared final (i.e. final classes cannot be extended).
public final class MyImmutable { � }

2.All its fields are final (final fields cannot be mutated once assigned).

 private final int[] myArray; 
    //do not declare as private final int[] myArray = null;

3.Do not provide any methods that can change the state of the immutable object in any way � not just setXXX methods, but any methods which can change the state.

4.The �this� reference is not allowed to escape during construction from the immutable class and the immutable class should have exclusive access to fields that contain references to mutable objects like arrays, collections and mutable classes like Date etc by:

�Declaring the mutable references as private.
�Not returning or exposing the mutable references to the caller (this can be done by defensive copying)

[Garrett Rowe]

i have a doubt.. please answer me immediately..

First of all Ease up.

how can i make a class immutable...??

In Java, a class is immutable if no methods are provided to mutate class level variables. Basically its easier to make a class immutable than mutable. Just don't provide any Mutator methods.

[Raghavan Muthu]

Hey,

Please go through this excellent article which speaks about

Mutable Vs Immutable Objects

How to make a class/object Immutable?

Hope this will help you to a good extent.
[ June 12, 2007: Message edited by: Raghavan Muthu ]