Java 8 中“System.out::println”有什么用
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What is the use of "System.out::println" in Java 8
提问by prime
I saw a code in java 8 to iterate a collection.
我在java 8中看到了一个代码来迭代一个集合。
List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
numbers.forEach(System.out::println);
What is the functionality of System.out::println? And how the above code can iterate through the List.
的功能是System.out::println什么？以及上面的代码如何遍历 List。
And what is the use of the operator ::, Where else we can use this operator ?
运算符的用途是::什么，我们还能在哪里使用这个运算符？
采纳答案by Konstantin Yovkov
It's called a "method reference"and it's a syntactic sugar for expressions like this:
它被称为“方法引用”，它是如下表达式的语法糖：
numbers.forEach(x -> System.out.println(x));
Here, you don't actually needthe name xin order to invoke printlnfor each of the elements. That's where the method reference is helpful - the ::operator denotes you will be invoking the printlnmethod with a parameter, which name you don't specify explicitly:
在这里，您实际上不需要名称x来调用println每个元素。这就是方法引用有用的地方 -::运算符表示您将println使用参数调用方法，您没有明确指定该名称：
numbers.forEach(System.out::println);
