JAVA8 之 Method References－Java in a Nutshell, 6th

JAVA8 的函数引用和 lambda表达式的关系＝＞函数引用是一种简化的 lambda表达式，只给出现有的函数，参数和返回值编译器推断去吧．

　其实这语法和 lambda表达式正好相反， lambda表达式表示匿名方法，就是没有函数名，只给出参数和方法体．那么现有的函数就派上用场了，现有的函数有方法名，给出方法名，参数和方法体都已经有了，由编译器推断出．

注：java中的方法不能独立存在，必须包含在类型中，这就是 lambda表达式 @FunctionalInterface的限制．

Recall that we can think of lambda expressions as methods that don’t have names.

Now, consider this lambda expression:

// In real code this would probably be shorter because of type inference

(MyObject myObj) -> myObj.toString()

This will be autoconverted to an implementation of a @FunctionalInterface that

has a single nondefault method that takes a single MyObject and returns String.

However, this seems like excessive boilerplate, and so Java 8 provides a syntax for

making this easier to read and write:

MyObject::toString

This is a shorthand, known as a method reference, that uses an existing method as a

lambda expression. It can be thought of as using an existing method, but ignoring

the name of the method, so it can be can used as a lambda, and autoconverted in the

usual way.