Java Concurrency - Immutable Object

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Immutable object in Java Concurrency.

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Rules

Don't provide “setter” methods — methods that modify fields or objects referred to by fields.
Make all fields final and private.
Don't allow subclasses to override methods. The simplest way to do this is to declare the class as final. A more sophisticated approach is to make the constructor private and construct instances in factory methods.
If the instance fields include references to mutable objects, don't allow those objects to be changed:
- Don't provide methods that modify the mutable objects.
- Don't share references to the mutable objects. Never store references to external, mutable objects passed to the constructor; if necessary, create copies, and store references to the copies. Similarly, create copies of your internal mutable objects when necessary to avoid returning the originals in your methods.

Library

com.google.common.collect (Guava)

List<Table> allTables = ImmutableList.copyOf(Table.values());

Builder Pattern with immutability ie final variable

final String value1;
final Boolean blue;

private Session(String value1, boolean isBlue)
{
   this.value1 = value1;
   this.isBlue = isBlue;
}

public Session withBlue(boolean isBlue)
{
  return new Session(
          this.value1,
          this.isBlue
  );
}

Collections

since Java10, Create new collection instances from existing instances

List.copyOf,
Set.copyOf,
and Map.copyOf .

Stream

Stream New methods toUnmodifiableList, toUnmodifiableSet, and toUnmodifiableMap have been added to the Collectors class in the Stream package.

Documentation / Reference

See Java Tuto - Immutable