package tree;

import java.util.Collection;

/**

* This class is used to represent the empty search tree: a search tree that

* contains no entries.

*

* This class is a singleton class: since all empty search trees are the same,

* there is no need for multiple instances of this class. Instead, a single

* instance of the class is created and made available through the static field

* SINGLETON.

*

* The constructor is private, preventing other code from mistakenly creating

* additional instances of the class.

*

*/

public class EmptyTree<K extends Comparable<K>, V> implements Tree<K, V> {

/**

* This static field references the one and only instance of this class. We

* won’t declare generic types for this one, so the same singleton can be used

* for any kind of EmptyTree.

*/

private static EmptyTree SINGLETON = new EmptyTree();

public static <K extends Comparable<K>, V> EmptyTree<K, V> getInstance() {

return SINGLETON;

}

/**

* Constructor is private to enforce it being a singleton

*

*/

private EmptyTree() {

// Nothing to do

}

public V search(K key) {

return null;

// throw new UnsupportedOperationException(“You must implement this method.”);

}

public NonEmptyTree<K, V> insert(K key, V value) {

Tree<K, V> leftTemp = EmptyTree.SINGLETON;

Tree<K, V> rightTemp = EmptyTree.SINGLETON;

return new NonEmptyTree<K, V>(key, value, leftTemp, rightTemp);

// throw new UnsupportedOperationException(“You must implement this method.”);

}

public Tree<K, V> delete(K key) {

return this;

// throw new UnsupportedOperationException(“You must implement this method.”);

}

public K max() throws TreeIsEmptyException {

throw new TreeIsEmptyException();

// throw new UnsupportedOperationException(“You must implement this method.”);

}

public K min() throws TreeIsEmptyException {

throw new TreeIsEmptyException();

// throw new UnsupportedOperationException(“You must implement this method.”);

}

public int size() {

return 0;

// throw new UnsupportedOperationException(“You must implement this method.”);

}

public void addKeysToCollection(Collection<K> c) {

return;

// throw new UnsupportedOperationException(“You must implement this method.”);

}

public Tree<K, V> subTree(K fromKey, K toKey) {

return this;

// throw new UnsupportedOperationException(“You must implement this method.”);

}

public int height() {

return 0;

// throw new UnsupportedOperationException(“You must implement this method.”);

}

public void inorderTraversal(TraversalTask<K, V> p) {

// Nothing to do

// throw new UnsupportedOperationException(“You must implement this method.”);

}

public void rightRootLeftTraversal(TraversalTask<K, V> p) {

// Nothing to do

// throw new UnsupportedOperationException(“You must implement this method.”);

}

}