如何从 Java8 lambda 创建 Runnable
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How Runnable is created from Java8 lambda
提问by robjwilkins
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.
我遇到了一些代码，尽管阅读了一些，但我仍然难以理解。有一个方法调用，它接受两个参数，其中一个是 Runnable。尽管有一个 lambda，而不是传入一个 Runnable 对象。
For example:
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();
}
}
}
}
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?
所以我的问题是，你能解释一下如何从 lambda 创建 Runnable 吗，也请有人解释一下语法()-> {}。具体来说，() 括号是什么意思？
thanks.
谢谢。
采纳答案by Pedro Affonso
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.
Lambda 可用于任何需要功能接口的地方。函数式接口是具有单个抽象方法的任何接口。
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.
在这种情况下使用的 lambda 语法是(arguments) -> {blockOfCodeOrExpression}. 在单个参数的情况下可以省略括号，在单个命令或表达式的情况下可以省略大括号。
In other words, () -> System.out.println("hello world");is equivalent* here where a Runnableis expected to
换句话说，() -> System.out.println("hello world");这里是等价的*，其中 aRunnable预期为
new Runnable(){
@Override
public void run(){
System.out.println("Hello world one!");
}
};
*(I'm pretty sure that it is not bytecode-equivalent, but is equivalent in terms of functionality)
*（我很确定它不是字节码等价的，但在功能方面是等价的）
