What is the purpose of “<<” (double less than) in groovy

Question

I saw in some of the code which I am unable to understand the purpose of << like in the following sample code

def renderFiles(args) {
   def model = []         


        

Answer 1

This is a leftShift operator. In groovy operator overloading is implemented, see here and the new docs for reference . In this particular case adding an element to list operation is overloaded.

Instead of:

model.add(createModel(fileArgs.id,fileArgs.path,fileArgs.ext))

You can simply write:

model << createModel(fileArgs.id,fileArgs.path,fileArgs.ext)

It's a kind of a shorthand. There are also other operators overridden for List class, e.g. plus(), minus(). See here.

Answer 2

In groovy << operator adds result of expression on the right side to the collection on the left side