minimum-depth-of-binary-tree java code

/**
* Definition for binary tree
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public int predepth(TreeNode root){
if(root==null){
return 0;
}
if(root.left==null){
return predepth(root.right)+1;
}
if(root.right==null){
return predepth(root.left)+1;
}
return Math.min(predepth(root.left),predepth(root.right))+1;
}
public int run(TreeNode root) {
return predepth(root);
}
}