Binary search tree

gistfile1.java

public class Main {
  public static void main(String args[]) {
    Tree<Integer> t = new Tree<Integer>();
    t.insert(20, 20);
    t.insert(10, 11);
    t.insert(40, 13);
    t.insert(30, 13);
    t.insert(25, 13);
    System.out.println(t);
    t.remove(30);
    System.out.println(t);
  }
}

class Tree<T> {
  int key;
  T value;
  Tree<T> left;
  Tree<T> right;
  public Tree(){};

  public void insert(int key, T value) {
    if (this.value == null) {
      this.key = key;
      this.value = value;
    } else {
      if (key < this.key) {
        if (left == null) {
          left = new Tree<T>();
        }
        left.insert(key, value);
      } else {
        if (right == null) {
          right = new Tree<T>();
        }
        right.insert(key, value);
      }
    }
  }

  public T get(int key) {
    if (this.value == null) {
      return null;
    } else if (this.key == key) {
      return value;
    } else if (key < this.key && left != null) {
      return left.get(key);
    } else if (key >= this.key && right != null) {
      return right.get(key);
    } else {
      return null;
    }
  }

  private Tree<T> getMinTree() {
    if (value != null) {
      if (left != null) {
        return left.getMinTree();
      } else {
        return this;
      }
    }
    return null;
  }

  public void remove(int key) {
    if (this.value == null) {
      return;
    }
    if (this.key == key) {
      if (left == null && right == null) {
        this.value = null;
        return;
      }
      Tree<T> s;
      if (left == null && right != null) {
        s = right;
      } else if (right == null && left != null) {
        s = left;
      } else {
        Tree<T> minTree = right.getMinTree();
        int tmpKey = minTree.key;
        T tmpVal = minTree.value;
        minTree.key = this.key;
        minTree.value = this.value;
        this.key = tmpKey;
        this.value = tmpVal;
        minTree.remove(key);
        return;
      }
      this.key = s.key;
      this.value = s.value;
      this.left = s.left;
      this.right = s.right;
    } else {
      if (key < this.key && left != null) {
        left.remove(key);
      } else if (key >= this.key && right != null) {
        right.remove(key);
      }
    }
  }

  public String toString() {
    if (value == null) {
      return "{}";
    }
    return "{" + key + ": [" + (left != null ? left.toString() : "null") + ", " + (right != null ? right.toString() : "null") + "]}";
  }
}