How can we create Immutable class in Java

There are many immutable classes like String, Boolean, Byte, Short, Integer, Long, Float, Double etc. In short, all the wrapper classes and String class is immutable. We can also create immutable class by creating final class that have final data members as the example given below

Steps to create immutable class:

1. The instance variable of the class is final i.e. we cannot change the value of it after creating an object.

2. The class is final so we cannot create the subclass.

3. There is no setter methods i.e. we have no option to change the value of the instance variable.

4. In the constructor we use the import org.joda.time.DateTime class. This is a better version than the java.util.Date because it is immutable. Using a java.util.Date would be dangerous as it is a mutable class and we can't control the calling thread (which might modify it).

Example: