Does Java have a `::` operator?

Question

Does Java have a :: operator? Please, do not close this question, I did search the docs and I'm sure it does not but I want to be completely sure.

I.e can there be something like MyClass::x or anything visually resembling that in Java.

Why are you asking this? It seems like a strange thing to ask; I've seen "what is this operator" questions and "what operator do I use" questions, but not "does any operator look like this". — user2357112, Dec 13 '13 at 09:38
http://stackoverflow.com/questions/20001427/double-colon-operator-in-java-8 — user2357112, Dec 13 '13 at 09:39
http://stackoverflow.com/questions/20001427/double-colon-operator-in-java-8 — AllTooSir, Dec 13 '13 at 09:41

score 7 · Answer 1 · answered Dec 13 '13 at 09:46

In Java 8 the operator :: has been introduced as a way to refer to a method. Basically, it turns the method into a first-class object, something you can pass to other methods as an argument, store in a variable, and return from a method.

This addition to the syntax is a part of the overall orientation towards the Functional Programming paradigm which is being introduced with Java 8. The elementary feature of FP are higher-order functions—such functions which accept other functions as argument, or return functions. This paradigm allows one to eliminate much boilerplate which now pervades the Java source code.

Philipp Sander · Accepted Answer · 2013-12-13T10:05:09.617

4

until and including Java 7: No!

Java 8: Yes!

simply as that.

edited Dec 13 '13 at 10:05

answered Dec 13 '13 at 09:41

Philipp Sander

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Rogue · Answer 3 · 2013-12-13T09:46:21.053

0

In Java 8 it allows for referencing of static members of a class, similar to PHP.

public class YourClass {

    public static int comparer(String one, String two){
        return one.length() - two.length();
    }

    public static void main(String[] args) {
        Arrays.sort(args, YourClass::comparer);
        //args are now sorted
    } 

}

As stated in comments, this is Java 8 (and later) only. JDK 7 and below does not have this.

edited Dec 13 '13 at 09:46

answered Dec 13 '13 at 09:40

Rogue

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I'm pretty sure that's not how you use it. There's already `YourClass.doSomething()` for that. – user2357112 Dec 13 '13 at 09:43
@MarkoTopolnik and user2357112 You are both correct, that was my own mistake having not used it yet myself. I'll update the answer – Rogue Dec 13 '13 at 09:44

sumit gupta · Answer 4 · 2013-12-13T10:31:53.350

-1

Upto Java 7 there is no double colon operator(::) in java as in C++. But Java 8 introduce double colon operator which is used to refer the methods.

Example(For Static Method)

public class TestClass {

    public void functionTest() {...}

}

We can call function 'functionTest()' by using double colon operator(::).

TestClass t=new TestClass();
t::functionTest

If 'functionTest()' is static then we can refer directly by using class name

TestClass::functionTest

There are four kinds of method references(as written in java doc)

For more information refer java doc

edited Dec 13 '13 at 10:31

answered Dec 13 '13 at 09:52

sumit gupta

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3

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The documentation you refer to contradicts your answer, which is because your answer is wrong. So you could learn something by reading the very document you are referring OP to. – Marko Topolnik Dec 13 '13 at 09:55
that was my mistake...now i think this is correct answer – sumit gupta Dec 13 '13 at 10:15
It is still wrong because the term "escape resolution" has nothing to do with Java---or with C++. BTW the downvote is not mine. – Marko Topolnik Dec 13 '13 at 10:20

Does Java have a `::` operator?

4 Answers4