Add leaf as well as non-leaf nodes at the same level in a GWT CellBrowser or Cell Tree

I want to add non-leaf as well as leaf nodes at a same level in a GWT CellBrowser/ Cell Tree. Can i do it? if yes, how? Because while returning DefaultNodeInfo I am not getting an option to return both kind of ListDataProviders.

A simple solution would be to create a superclass or interface Node, which your NonLeafNode and your LeafNode class extend / implement:

public class NonLeafNode extends Node{
}

or

public class NonLeafNode implements Node{
}

Then you can give the CellBrowser or CellTree a single ListDataProvider which provides both types of node. In the underlying model, e.g. a TreeViewModel, you need to adjust the isLeaf(Object o) and the getNodeInfo(T value) functions as follows:

public boolean isLeaf(Object value) {
    if (value instanceof NonLeafNode) return true;
    if (value instanceof LeafNode) return false;
    return false;
}

public <T> getNodeInfo(T value){
    if (value instanceof NonLeafNode) 
         // return node info for non-leaf-node
        ;
    else if (value instanceof LeafNode)
         // return node info for leaf node
        ;
    return null;
}