是否有Java中的Objective-C块之类的东西? [英] Is there anything like an Objective-C block in Java?

问题描述

我只是在学习Java，并且之前我已经在Objective-C中开发了应用程序.我喜欢块"的概念，因为它们允许代码在发生某些事情后运行.

I'm just learning Java, and I've developed apps in Objective-C before. I like the concept of "blocks", because they allow code to be ran after something happens.

例如，要在SpriteKit应用程序中经过一定时间后执行一个块，该应用程序会从场景myScene调用方法helloWorld:

For example, to execute a block after a certain amount of time in a SpriteKit app that calls a method helloWorld from scene myScene:

[myScene runAction:[SKAction sequence:@[[SKAction waitForDuration:5], [SKAction runBlock:^{
    [myScene helloWorld];
}]]]];

Java中是否有类似于块的内容?如果是这样，我将如何使用它? ...的语法是什么?

Is there anything like a block in Java? If so, how would I use it? What's the syntax to...

• 将其用作函数参数吗?
• 在函数中调用所说的块吗?
• 为块分配一个值吗?

我听说过一些关于关闭器"的信息，但是我不确定它们是什么或如何使用它们.

I've heard a little bit about "closures," but I'm not so sure what they are or how to use them.

推荐答案

在Java中，执行此操作的方法是使用接口.最基本的接口是Runnable，它具有方法run.

In Java, the way to do this is to use an interface. The most basic interface for this is Runnable which has a method run.

...的语法是什么

What's the syntax to...

将其用作函数参数吗?

void foo(Runnable r)

调用函数中的所说的块吗?

call said block in the function?

r.run();

为块分配一个值?

assign a value to the block?

在Java 8之前，您必须执行以下操作:

Before Java 8 you had to do something like this:

Runnable r = new Runnable() {
    @Override
    public void run() {
        // do something
    }
}

现在您可以这样做:

Runnable r = () -> { // do something }

包含->的表达式称为lambda.刹车()是您可以编写任何参数的位置，但是Runnable的方法run没有任何参数.您也可以将Runnable传递给方法，而无需提及Runnable:

An expression involving -> is called a lambda. The brakets () are where you would write any parameters, but the method run of Runnable doesn't have any parameters. You can also pass a Runnable to a method without mentioning Runnable:

foo(() -> { // do something });

Java 8引入了许多新接口，其中该方法可以返回值或接受参数.

Java 8 introduced many, many new interfaces where the method can return a value or accept parameters.

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