如何从Java8 lambda创建Runnable [英] How Runnable is created from Java8 lambda

问题描述

我遇到了一些代码，尽管有点阅读，但我还是很难理解。调用一个方法，该方法接受两个args，其中一个是Runnable。而不是传递一个Runnable对象虽然有一个lambda。

I've come across some code which I'm struggling to understand despite a bit of reading. There is a call to a method which takes in two args, one of which is a Runnable. Rather than passing in a Runnable object though there is a lambda.

例如：

public class LambdaTest {

    private final Lock lock = new ReentrantLock();

    @Test
    public void createRunnableFromLambda() {
        Locker.runLocked(lock, () -> {
            System.out.println("hello world");
        });
    }

    public static class Locker {
        public static void runLocked(Lock lock, Runnable block) {
            lock.lock();
            try {
                block.run();
            } finally {
                lock.unlock();
            }
        }
    }
}

所以我的问题是，你能解释一下吗？如何从lambda创建Runnable，还有人可以解释语法（） - > {}。具体来说，（）括号是什么意思？

So my question is, can you explain how a Runnable is created from the lambda, and also please could someone explain the syntax () -> {}. Specifically, what do the () brackets mean?

谢谢。

推荐答案

Lambda可以在任何需要功能接口的地方使用。
功能接口是具有单个抽象方法的任何接口。

A Lambda can be used in any place where a functional interface is required. A functional interface is any interface with a single abstract method.

在这种情况下使用的lambda语法是（参数） - > ; {blockOfCodeOrExpression} 。在单个参数的情况下可以省略括号，并且在单个命令或表达式的情况下可以省略括号。

The lambda syntax used in this case is (arguments) -> {blockOfCodeOrExpression}. The parenthesis can be omitted in the case of a single argument, and the braces can be omitted in the case of a single command or expression.

换句话说，（） - > System.out.println（hello world）; 相当于*到

 new Runnable(){      
   @Override
   public void run(){
     System.out.println("Hello world one!");
   }
 };

（我很确定它不是字节码等价的，但在功能方面是等价的）

(I'm pretty sure that it is not bytecode-equivalent, but is equivalent in terms of functionality)

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