What does ()->{} represent in java?

Question

What does ()->{} represent in java?. Any help would be highly appreciated.

Possible duplicate of [What does the arrow operator, '->', do in Java?](http://stackoverflow.com/questions/15146052/what-does-the-arrow-operator-do-in-java) — Suraj Rao, Apr 29 '17 at 06:38
You should at least show us this in the context of some actual code. — Tim Biegeleisen, Apr 29 '17 at 06:38
It's a "lambda", a way of representing functions, or in Java's case, anonymous implementations of functor interfaces. — Lew Bloch, Apr 29 '17 at 06:43
Extremely sorry for that . I have seen this operator in many function calls, so I thought it is general one. Latest encounter in the following function call executorService.execute(() -> { sqs.receiveMessage(); processMessage(); }); — Vivek Kumar, Apr 29 '17 at 06:43

score 4 · Answer 1 · answered Apr 29 '17 at 06:43

4

It's a lambda expression, basically a concise way of writing a function. ()->{} is a function that takes no arguments and does nothing. A longer way of writing the same thing:

new Runnable() {
    @Override
    public void run() {
        // nothing
    }
};

answered Apr 29 '17 at 06:43

takteek

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Why would someone write a function that does **nothing**? – TDG Apr 29 '17 at 06:46
2

It could actually be useful as a NOOP default value for something. E.g. an optional callback because if the default is `()->{}` then you don't need to check for null. Basically the Null Object pattern – takteek Apr 29 '17 at 07:03

score 0 · Answer 2 · edited May 23 '17 at 11:54

Let's consider old way of writing functions(i.e methods) in java.

//lets assume this is inside calculate class
public int sum(int a, int b){
     return a+b;
}

in java 8 we have something called lambda's in which we have concept called passing behaviours(methods) to another behaviour(methods).

in those case we use syntax like (a,b) -> return a+b;

BiFunction<Integer,Integer,Integer> sum= (a,b)->{
            return a+b;
        };

System.out.println(sum.apply(1, 2));

Even we can store Function in a variable and pass to another function. you can see here

now lets see about syntax (a,b) ->{ return a + b}; (a,b) are arguments to function;

and the line of code inside {} represent the behaviour. -> is to separate both left and right expressions.

you can explore more about java8 and lambda over here

What does ()->{} represent in java?

2 Answers2