syntax - What do curly braces in Java mean by themselves?

Question

I have some Java code that uses curly braces in two ways

// Curly braces attached to an 'if' statement:
if(node.getId() != null)
{
    node.getId().apply(this);
}

// Curly braces by themselves:
{
    List<PExp> copy = new ArrayList<PExp>(node.getArgs());
    for(PExp e : copy)
    {
        e.apply(this);
    }
}
outAMethodExp(node);

What do those stand-alone curly braces after the first if statement mean?

Answer 1

The only purpose of the extra braces is to provide scope-limit. The List<PExp> copy will only exist within those braces, and will have no scope outside of them.

If this is generated code, I assume the code-generator does this so it can insert some code (such as this) without having to worry about how many times it has inserted a List<PExp> copy and without having to worry about possibly renaming the variables if this snippet is inserted into the same method more than once.