Does Java have a `::` operator? [duplicate]

Question

This question already has answers here:

:: (double colon) operator in Java 8 (17 answers)

Closed 12 years ago.

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.

• Alexander: But, dear sir, does it or does it not though?
• Boris the Spider: Short answer, yes. In Java 8.
• Gimby: "In Java 8". So right now, no it doesn't.
• user2357112: 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: stackoverflow.com/questions/20001427/…

Answer 1

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.

Answer 2

until and including Java 7: No!

Java 8: Yes!

simply as that.

Answer 3

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.

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

Answer 4

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

• Marko Topolnik: 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.
• sumit gupta: that was my mistake...now i think this is correct answer
• Marko Topolnik: It is still wrong because the term "escape resolution" has nothing to do with Java---or with C++. BTW the downvote is not mine.