Java 8：方法引用Bound Receiver和UnBound Receiver之间的区别 [英] Java 8: Difference between method reference Bound Receiver and UnBound Receiver

问题描述

我正在尝试在我的代码中使用Java 8方法引用。有四种类型的方法参考可用。

I am trying to use Java 8 method references in my code. There are four types of method references available.

1. 静态方法参考。


2. 实例方法（绑定接收器）。


3. 实例方法（UnBound接收器）。


4. 构造函数引用。

1. Static method reference.
2. Instance Method (Bound receiver).
3. Instance Method (UnBound receiver).
4. Constructor reference.

随附静态方法引用和构造函数引用我没有问题，但实例方法（绑定接收器） 和实例方法（UnBound接收器）让我很困惑。在 Bound 接收器中，我们使用Object引用变量来调用如下方法：

With Static method reference and Constructor reference i have no problem, but Instance Method (Bound receiver) and Instance Method (UnBound receiver) really confused me. In Bound receiver, we are using an Object reference variable for calling a method like:

objectRef::Instance Method

在 UnBound 接收器我们使用类名来调用如下方法：

In UnBound receiver we are using Class name for calling a method like:

ClassName::Instance Method.

我有以下问题：

1. 对实例方法的不同类型的方法引用有什么需要？


2. Bound 和未绑定接收方法引用？


3. 我们应该在哪里使用 Bound 接收方我们应该在哪里使用 Unbound 接收器？

1. What is the need for different types of method references for Instance Methods?
2. What is the difference between Bound and Unbound receiver method references?
3. Where should we use Bound receiver and where should we use Unbound receiver?

我也找到了解释来自绑定和未绑定接收器？ ID = TnU_BAAAQBAJ&安培; PG = PA154&安培; LPG = PA154&安培; DQ = java的％208％20method％20reference％20unbound％20于是％20bound&安培;源= BL&安培; OTS = VZt9o58Bwg&安培; SIG = KucWWaGHAfcCoir3Sks3WWsUx-S&安培; HL = EN&安培; SA = X&安培; ved = 0ahUKEwjBuKe09bXLAhXCj44KHWiZAYAQ6AEISTAH #v = onepage& q = java％208％20method％20reference％20unbound％20and％20bound& f = falserel =nofollow noreferrer> Java 8语言功能书籍，但仍然与实际的骗局CEPT。

I also found the explanation of Bound and Unbound receiver from Java 8 language features books, but was still confused with the actual concept.

推荐答案

unBound接收器的想法，例如 String :: length 是你指的是对象的
方法，将作为lambda 的一个参数提供。例如，
lambda表达式（String s） - > s.toUpperCase（）可以重写为 String :: toUpperCase 。

The idea of unBound receiver such as String::length is that you’re referring to a method to an object that will be supplied as one of the parameters of the lambda. For example, the lambda expression (String s) -> s.toUpperCase() can be rewritten as String::toUpperCase.

但是Bounded指的是当您将
lambda中的方法调用已存在的外部对象时的情况。例如，lambda表达式（） - >
expensiveTransaction.getValue（）可以重写为 expensiveTransaction :: getValue 。

But Bounded refers to a situation when you’re calling a method in a lambda to an external object that already exists. For example, the lambda expression () -> expensiveTransaction.getValue() can be rewritten as expensiveTransaction::getValue.

三种不同方法参考方式的情况

Situations for three different ways of method reference

（args） - > ClassName.staticMethod（args）
可以是 ClassName :: staticMethod

（arg0，rest） - > arg0.instanceMethod（rest）
可以是 ClassName :: instanceMethod （ arg0 的类型为 ClassName ）

（args） - > expr.instanceMethod（args）
可以是 expr :: instanceMethod

在Action Book

Answer retired from Java 8 in Action book

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