Tree Implementations - Data Structures and Abstractions with Java - page 601

An Interface for a Node
24.2

Listing 24-1 contains a Java interface for a class of nodes suitable for a binary tree. We place the
interface in the package TreePackage and omit its access modifier. Without this modifier, the inter-
face is accessible only by classes within TreePackage .

LISTING 24-1

An interface for the nodes in a binary tree

package TreePackage;
interface BinaryNodeInterface<T>
{

/** Retrieves the data portion of this node.
@return the object in the data portion of the node */
public T getData();

/** Sets the data portion of this node.
@param newData the data object */
public void setData(T newData);

/** Retrieves the left child of this node.
@return the node that is this node's left child */
public BinaryNodeInterface<T> getLeftChild();

/** Retrieves the right child of this node.
@return the node that is this node's right child */
public BinaryNodeInterface<T> getRightChild();

/** Sets this node's left child to a given node.
@param leftChild a node that will be the left child */
public void setLeftChild(BinaryNodeInterface<T> leftChild);

/** Sets this node's right child to a given node.
@param rightChild a node that will be the right child */
public void setRightChild(BinaryNodeInterface<T> rightChild);

/** Detects whether this node has a left child.
@return true if the node has a left child */
public boolean hasLeftChild();

/** Detects whether this node has a right child.
@return true if the node has a right child */
public boolean hasRightChild();

/** Detects whether this node is a leaf.
@return true if the node is a leaf */
public boolean isLeaf();

/** Counts the nodes in the subtree rooted at this node.
@return the number of nodes in the subtree rooted at this node */
public int getNumberOfNodes();

/** Computes the height of the subtree rooted at this node.
@return the height of the subtree rooted at this node */
public int getHeight();