java - Binary Tree Deleting a node -

below code wrote case when deleteitem @ leaf node. if equating found leaf node "null" when print inorder traversing order if tree, element not deleted , comes on screen. missing?

public void deletenode(t deleteitem)     {         treenode<t> node = root;         if(root == null)         {             system.out.print("binary tree not exist");             system.exit(0);         }         while((node.data != deleteitem) && (node.leftnode != null || node.rightnode != null))         {             if(deleteitem.compareto(node.data)<0)                 node = node.leftnode;             else                 node = node.rightnode;         }         //system.out.printf("deleting item is: %s\n", node.data);         if(node.data != deleteitem)         {                system.out.println("\ndeleteitem not found in tree");             system.exit(0);         }         else         {             if(node.leftnode == null && node.rightnode == null)             {                 node = null;             }         }     } 

java "pass-by-value", treenode<t> tmp = root here means assigning tmp's references root means have 2 different references same instance. according when node = null set local references null means node's parent still reference it. remove leaf node tree need keep track of parent , removing reference node (removed reference in tree not local copy) that:

public void deletenode(t deleteitem) {         treenode<t> node = root;         treenode<t> parent = null; // parent of deleted node.         if(root == null) {             system.out.print("binary tree not exist");             system.exit(0);         }         while((node.data != deleteitem) &&                (node.leftnode != null || node.rightnode != null)) {             parent = node; // keep track of parent of deleted node             if(deleteitem.compareto(node.data) < 0)                 node = node.leftnode;             else                 node = node.rightnode;         }         if(node.data != deleteitem) {                system.out.println("\ndeleteitem not found in tree");             system.exit(0);         }         else {             if(parent.leftnode == node)                 parent.leftnode = null;             else                 parent.rightnode = null;         }     }