Java 通过 lambda 表达式调用 System.out.println()
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/23554413/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Calling System.out.println() through a lambda expression
提问by λ Jonas Gorauskas
In C# I can write the following code:
在 C# 中，我可以编写以下代码：
public static Action<object> WL = x => Console.WriteLine(x);
... and then every time that I want to write something out to the console I just call:
...然后每次我想向控制台写一些东西时，我只需要调用：
WL("Some output");
What would be the equivalent code using Java 8 lambda expressions? I tried the following and it does not work:
使用 Java 8 lambda 表达式的等效代码是什么？我尝试了以下方法但它不起作用：
static void WL = (String s) -> { System.out.println(s); }
采纳答案by Jon Skeet
Your current attempt doesn't work because you're trying to declare a variable of type void- the equivalent would fail in C# too. You need to declare a variable of a suitable functional interface, just like you use a delegate type in C#.
您当前的尝试不起作用，因为您试图声明一个类型的变量void- 在 C# 中等效也会失败。您需要声明一个合适的函数式接口的变量，就像您在 C# 中使用委托类型一样。
You can do it with a lambda expression, but it would be cleaner (IMO) to use a method reference:
您可以使用 lambda 表达式来完成，但使用方法引用会更清晰（IMO）：
import java.util.function.Consumer;
public class Test {
public static void main(String[] args) {
Consumer<Object> c1 = x -> System.out.println(x);
Consumer<Object> c2 = System.out::println;
c1.accept("Print via lambda");
c2.accept("Print via method reference");
}
}
Here the Consumer<T>interface is broadly equivalent to the Action<T>delegate in .NET.
这里的Consumer<T>接口大致相当于Action<T>.NET 中的委托。
Similarly you can use a method group conversion in C# rather than a lambda expression:
同样，您可以在 C# 中使用方法组转换而不是 lambda 表达式：
public static Action<object> WL = Console.WriteLine;
回答by Vince Emigh
interface MyMethod {
public void print(String s);
}
class Main {
public static void main(String[] args) {
MyMethod method = (String s) -> { };
}
}
In java, lambda expressions revolve around functional interfaces; interfaces only containing one method.
在java中，lambda表达式围绕着函数式接口；接口只包含一种方法。
