TreeHeight

Task description
In this problem we consider binary trees, represented by pointer data-structures. A pointer is called a binary tree if:
it is an empty pointer (it is then called an empty tree); or
it points to a structure (called a node) that contains a value and two pointers that are binary trees (called the left subtree and the right subtree).
A figure below shows a tree consisting of six nodes.
A path in a binary tree is a sequence of nodes one can traverse by following the pointers. More formally, a path is a sequence of nodes P[0], P[1], ..., P[K], such that node P[L] contains a pointer pointing to P[L + 1], for 0 ≤ L < K. K is called the length of such a path.
The height of a binary tree is defined as the length of the longest possible path in the tree. In particular, a tree consisting only of just one node has height 0 and the height of an empty tree is undefined.
For example, consider the following tree:

Subtrees of nodes D, E and F are empty trees. Sequence A, B, E is a path of length 2. Sequence C, F is a path of length 1. Sequence E, B, D is not a valid path. The height of this tree is 2.
Assume that the following declarations are given:
class Tree {
  public int x;
  public Tree l;
  public Tree r;
}
Write a function:
class Solution { public int solution(Tree T); }
that, given a non-empty binary tree T consisting of N nodes, returns its height.
For example, given tree T shown in the example above, the function should return 2.
Assume that:
N is an integer within the range [1..1,000].
Complexity:
expected worst-case time complexity is O(N);
expected worst-case space complexity is O(N).

Solution:
// you can also use imports, for example:
// import java.math.*;
class Solution {
    public int solution(Tree T){
        return solution(T, T);
    }
    public int solution(Tree T, Tree root) {
        // write your code in Java SE 7
        
        if(T==null)
        return 0;
        
        int lheight=0, rheight=0;
        lheight=solution(T.l, root);
        rheight=solution(T.r, root);
        if(T==root)
        return Math.max(lheight,rheight);
        else
        return Math.max(lheight+1,rheight+1);
        
        
        
    }
}