Binary Tree Maximum Path Sum

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    
    private static int max;
    public int maxPathSum(TreeNode root) {
        // Start typing your Java solution below
        // DO NOT write main() function
        max=-100000;
        dfs(root);
        return max;
    }
    private int dfs(TreeNode node){
        if(node==null)return 0;
        int local_max=node.val;
        //node_max = dfs(node.left,max) > 0
        int leftmax = dfs(node.left);
        int rightmax = dfs(node.right);
        if( leftmax > 0)local_max += leftmax;
        if( rightmax > 0)local_max += rightmax;
        if(max<local_max) max = local_max;
        
        return node.val+Math.max(Math.max(0, leftmax), rightmax);
    } 
}