How to return a generic type in Java AST

I am writing a program to modify Java abstract syntax tree (AST), but I don't know how to generate a generic return type. Who can help me?

The generated method looks like this:

public static List<String> converter() {
     return new ArrayList<String>();
}

I'm using com.sun.tools.javac.tree.TreeMaker.MethodDef() to generate a method's JCTree, like this:

return treeMaker.MethodDef(
                modifiers,
                method,
                returnType,
                List.nil(),
                List.nil(),
                List.nil(),
                methodBody,
                null
        );

All is well, but the problem is the 'returnType' parameter

It is a JCExpression type, which I can only set to 'java.util.List'.

How do I set it to List<String>?

PLEASE HELP ME!!! Somebody Help Me?