private boolean isSumTree(Node root,Count count){
        if(root == null){
            return true;
        }
        if(root.left == null && root.right == null){
            count.size = root.data;
            return true;
        }
        Count leftCount = new Count();
        Count rightCount = new Count();
        boolean isLeft = isSumTree(root.left,leftCount);
        boolean isRight = isSumTree(root.right,rightCount);
        count.size = root.data + leftCount.size + rightCount.size;
        return isLeft && isRight && root.data == (leftCount.size + rightCount.size);
    }
http://www.geeksforgeeks.org/check-if-a-given-binary-tree-is-sumtree/
A SumTree is a Binary Tree where the value of a node is equal to sum of the nodes present 
in its left subtree and right subtree
src/com/interview/tree/SumTree.java