Simple Binary Tree in Java in just one class -

i have implement simple binary tree. need put , get method. if key in use have replace value. code i'm very unsure if working right... can confirm code work? sorry... don't know how debug such class... :/ , no - not homework. template course learn java... ;)

//don't import other classes. public class binarytree<k extends comparable<k>, v> {      //please don't add further attributes.     private k key;     private v value;     private binarytree<k, v> left;     private binarytree<k, v> right;      /**      * class binary tree-based collection key-value-pairs.      */     public static void main(string[] args) {       binarytree<integer, string> treeinteger = new binarytree<>(2, "two ");       treeinteger.put(1, "one ");       treeinteger.put(0, "zero ");       treeinteger.put(3, "three ");       treeinteger.put(6, "six ");       treeinteger.put(3, "threenew ");           system.out.println(tree.tostring());          if (tree.get(4) == null) {             system.out.println("null");         }     }      public binarytree(k key, v value) {         //fill in solution here.         this.key = key;         this.value = value;     }      public void put(k key, v value) {         //fill in solution here.         if (this.key.compareto(key) > 0 ) {             // links             if (this.left == null) {                 this.left = new binarytree<>(key, value);             } else {                 left.put(key, value);             }         } else if (this.key.compareto(key) < 0) {             if (this.right == null) {                 this.right = new binarytree<>(key, value);             } else {                 this.right.put(key, value);             }         } else if (this.key.compareto(key) == 0) {             this.key = key;             this.value = value;         }     }      public v get(k key) {         //fill in solution here.         if (this.key.compareto(key) > 0 && this.left != null) {             return this.left.get(key);         } else if (this.key.compareto(key) < 0 && this.right != null) {             return this.right.get(key);         } else if (this.key.compareto(key) == 0 && this.value != null) {             return this.value;         } else if (this.key == key) {             return value;         }          return null;     } } 

my own touring

    string s = "";      if (left != null) {         s += left.tostring();     }      if (value != null) {         s += value.tostring();     }      if (right != null) {         s += right.tostring();     }      return s; 

add , test:

@override public string tostring() {      if(this.left==null&&this.right != null){         return this.value.tostring()+" " + this.right.tostring();     }      if(this.left!=null&&this.right == null){         return this.value.tostring()+" " + this.left.tostring();     }       if(this.left !=null && this.right != null)     return this.value.tostring()+" " + this.left.tostring()                 +" " + this.right.tostring();     return this.value.tostring();; } 

this preorder tree traversal prints nodes in tree. if create tree correctly, should able print values.

to print in ascending order, use in-order tree traversal:

@override public string tostring() {      if(this.left==null&&this.right != null){         return this.value.tostring()+" " + this.right.tostring();     }      if(this.left!=null&&this.right == null){         return  this.left.tostring() +" " + this.value.tostring();     }       if(this.left !=null && this.right != null)     return this.left.tostring()                 +" " +this.value.tostring()+" "  + this.right.tostring();     return this.value.tostring(); }