How does one return from a groovy closure and stop its execution?

Question

I would like to return from a closure, like one would if using a break statement in a loop.

For example:

largeListOfElements.each{ element->
             


        

Answer 1

After paulmurray's answer I wasn't sure myself what would happen with an Exception thrown from within a closure, so I whipped up a JUnit Test Case that is easy to think about:

class TestCaseForThrowingExceptionFromInsideClosure {

    @Test
    void testEearlyReturnViaException() {
        try {
            [ 'a', 'b', 'c', 'd' ].each {                 
                System.out.println(it)
                if (it == 'c') {
                    throw new Exception("Found c")
                } 
            }
        }
        catch (Exception exe) {
            System.out.println(exe.message)
        }
    }
}  

The output of the above is:

a
b
c
Found c

But remember that "one should NOT use Exceptions for flow control", see in particular this Stack Overflow question: Why not use exceptions as regular flow of control?

So the above solution is less than ideal in any case. Just use:

class TestCaseForThrowingExceptionFromInsideClosure {

    @Test
    void testEarlyReturnViaFind() {
        def curSolution
        [ 'a', 'b', 'c', 'd' ].find {                 
            System.out.println(it)
            curSolution = it
            return (it == 'c') // if true is returned, find() stops
        }
        System.out.println("Found ${curSolution}")
    }
}  

The output of the above is also:

a
b
c
Found c