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Question

I am new to Groovy. I execute the following Groovy code:

myList=[234, 34, "Stackoverflow", 3.14]

myList=myList.collect {if (it instanceof Integer) it*it}     

println myList

it outputs:

[54756, 1156, null, null]

It seems to me that it shouldn't change the strings value. when I change the second line to:

myList=myList.collect {if (it instanceof Integer) it*it else it=it}

it works as I expected:

[54756, 1156, Stackoverflow, 3.14]

I am wondering what is the logic behind that!

Answer 1

Since there is no else clause in your first version, null is the result.

The second version should work like this, too:

myList.collect {if (it instanceof Integer) it * it else it}

Answer 2

I guess that the reason is because you have not specified the outcome of the first closure in case an element is not an Integer and it defaulted to null

​println a()

def a() {
   if (1==2) "Hello!"
}​

>> null