Java Final Keyword

Keyword final can be used in three different ways:

1. final variable

2. final method

3. final class

1. final variable 基本上就是 constant，一旦被赋值，就不能被变更；如果在class里declare a final variable, 那么在此class生成出的object就必须对这个 final variable赋值。

2. final method 是method can't be over overridden.

3. final class is a class can't be inherited.