Java8 new feature (c) of the method and the references cited constructor

1. Scene

　　To be transmitted to the operator when the body Lambda implemented methods already exist, a reference method can be used. (Abstract method parameter list must reference the method's parameter list and methods consistent)

2. Grammar

　　:: operator [] used to separate the method name and the name of the object or class. The three main use cases:

　　1) Object instance method ::

　　2) :: class static method

　　3) Examples of the method class ::

3. The method of using a reference

　　1) (x) -> System.out.println (x); equivalent to System.out :: println;

　　2）