Adding two ArrayLists to JTree

Question

everything seems to run fine apart from the if statement, comments in code explain most of it.

The aim is to add two ArrayLists to a Jtree. Arraylist containing whole numbers like (1,2,3,4 etc) and the second containing double number like (1.1,1.2,2.1 etc).

I want to add the first array to the JTree, which i have managed to do. But i then want to add the second arraylist so thats it is a child of the first.

So that 1.1 and 1.2 are a child of 1 and 2.1 is a child of 2 etc.

Any help would be appreciated.

    DisplayTree.addActionListener(new ActionListener() {

        @Override
        public void actionPerformed(ActionEvent e) {

            JFrame frameG2 = new JFrame("Cell Tree");
            frameG2.setSize( 400, 900 );
            frameG2.setVisible(true);

            frameG2.setBackground( Color.gray );

            DefaultMutableTreeNode root = new DefaultMutableTreeNode("cells");

            int i=0;
            //should through first array list and adds it to root
            for (int n =0; n<arrayList.size();n++) {
                DefaultMutableTreeNode cells = new DefaultMutableTreeNode(arrayList.get(n));

                root.add(cells);

                //should go through jtree elements
                Enumeration search = root.postorderEnumeration();
                while(search.hasMoreElements()){


                    //should compare each element to a 2nd array
                    //2nd array consists of double numbers like 1.1,1.2,2.1 etc
                    //so i split it before the "." so 1.1 is 1
                    //first array consists of whole numbers like 1, 2, 3
                    //want to make 1.1 child of 1 etc.
                    if (search.nextElement().toString()==(arrayList2.get(i).toString().split("\\.", 0)[0])) {
                        DefaultMutableTreeNode NewCells = new DefaultMutableTreeNode(arrayList2.get(i));
                        cells.add(NewCells);

                        i++;

                    }else{
                    }

                }
            }


                tree = new JTree(root);
                frameG2.add(tree);


        }
    });