Question

I was reading that there are many reasons for making a class final in SO threads and also in an arcticle
Two of which were

1. To remove extensibility
2. to make class immutable.

Does making a class immutable have the characteristic along with it as being final ( it’s methods )? I don’t see the difference between the two?

Answer 1

Immutable object does not allow to change his state. Final class does not allow to inherit itself. For example class Foo (see below) is immutable (the state, ie _name is never changed ) and class Bar is mutable (rename method allows to change the state):

final class Foo
{
  private String _name;

  public Foo(string name)
  {
    _name = name;
  }

  public String getName()
  {
    return _name;
  }
}

final class Bar
{
  private String _name;

  public Bar(string name)
  {
    _name = name;
  }

  public String getName()
  {
    return _name;
  }

  public void rename(string newName)
  {
    _name = newName;
  }
}