mistake

[Andrew Lit]

Hallo,
Here is the realization of AVL tree:

  
import java.util.*;
public class Tree {
private String s;
public Link root = null;
public Link main = null;
  public Tree(String s) {
   this.s=s;
  }
  public void init_tree(){
    for(int i=0;i<s.length();i++){
     object temp = new object(s.charAt(i),i);
        insert(temp);
    }
    print(root); /// i get infinity loop
  }
  public void insert(object Obj){
   Link next_left = null; Link next_right = null;
     if (root==null){root= new Link(Obj);
                     root.left = new Link();
                     root.right = new Link();
                     root.value.height = 0;
                     main=root;
                  }
     if (root.value.index >Obj.index){
                                next_right = new Link(Obj);
                                root.right=next_right;
              if ((define_height(root.right)-define_height(root.left))==2){
                if(root.value.index<root.right.value.index) turn_left(root);
                                    else double_left(root);
              }else root.value.index=max(define_height(root.left),define_height(root.right))+1;
     }
             else{
              next_left= new Link(Obj);
              root.left=next_left;
              root.right = new Link();
              if ((define_height(root.left)-define_height(root.right))==2){
                if(root.value.index<root.left.value.index) turn_right(root);
                                    else double_right(root);
              }else root.value.index=max(define_height(root.left),define_height(root.right))+1;
             }
  }
  public void turn_left(Link tree){
     Link temp;
     temp=tree.right;
     tree.right=temp.left;
     temp.left=tree;
     root.value.height = max(define_height(tree.left),define_height(tree.right))+1;
     temp.value.height = max(define_height(tree.left),define_height(tree.right))+1;
     tree=temp;
  }
  public void turn_right(Link tree){
    Link temp;
    temp=tree.left;
    tree.left=temp.right;
    temp.right=tree;
    tree.value.height = max(define_height(tree.left),define_height(tree.right))+1;
    temp.value.height = max(define_height(tree.left),define_height(tree.right))+1;
    tree=temp;
  }
  public void double_left(Link tree){
     turn_right(tree.right);
     turn_left(tree);
  }
  public void double_right(Link tree){
    turn_left(tree.left);
    turn_right(tree);
  }
  public int max(int i,int j){
      return i>=j?i:j;
  }
  public int define_height(Link tree){
    return tree.value.height;
  }
  public void print(Link local){
    while ((local.left!=null)&(local.right!=null)){
      print(local.left);
      System.out.println(local.value.c);
      print(local.right);
    }
  }
}

 import java.util.*;
public class Link {
protected Link left =null;
protected Link right = null;
protected object value;
  public Link(object value) {
    this.value=value;
  }
  public Link(){
    value = new object();
  }
} 

 public class object extends java.lang.Object {
protected char c;
protected int index;
protected int height=0;
  public object(char c,int index){
   this.c=c;
   this.index=index;
  }
  public object(){
   height=0;
  }
} 

Elemnts are inserted into the tree according the value of "index" and the variable height supposed to check if the structure of AVL tree is ok. My problem is that the next element is null, it is not filled. I suppose that problem is in variable height but i am not able to fix it no matter that i spend quite a lot of time on it. so i decided to post it here. I hope that you will help me in finding the mistake. I would be really appreciated.