【Java 学习- final keyword

If the case of a compile-time constant, the compiler is allowed to "fold" the constant value into any calculations in which it's used; that is, the calculation can be performed at compile time, eliminating some run-time overhead. In Java, these sorts of constants must be primitives and are expressed with the final keyword. A value must be given at the time of definition of such a constant.

A field that is both static and final has only one piece of storage that cannot be changed.

With a primitive, final makes the value a constant, but with an object reference, final makes the reference a constant. Once the reference is initialized to an object, it can never be changed to point to another object. However, the object itself can be modified.