How to create immutable class in java?

How to create immutable class in java?

The key points for immutable are:

• no setters methods
• make variables private and final
• return lists using Collections.unmodifiableList - never return any mutable field; always return either a copy (deep if appropriate) or an immutable version of the field
• make class final
• if variables are changed internally in the class this change is not visible and has no effect outside of the class (including affecting things like equals() and hashcode()).

Resource Link:

1. How to create immutable class in java
2. https://www.infoq.com/presentations/Are-We-There-Yet-Rich-Hickey