chapter 16 data structures 1 ©2000, john wiley & sons, inc. horstmann/java essentials, 2/e...

©2000, John Wiley & Sons, Inc.Horstmann/Java Essentials, 2/e

Chapter 16 Data Structures1

Chapter 16

An Introduction to Data Structures



Figure 1Inserting an Element Into aLinked List



Figure 2A List Iterator



Figure 3A Conceptual Viewof the List Iterator



Program ListTest1.java

import java.util.LinkedList;import java.util.ListIterator;

public class ListTest1{ public static void main(String[] args) { LinkedList staff = new LinkedList(); staff.addLast("Dick"); staff.addLast("Harry"); staff.addLast("Romeo"); staff.addLast("Tom");

// | in the comments indicates the iterator position

ListIterator iterator = staff.listIterator(); // |DHRT iterator.next(); // D|HRT iterator.next(); // DH|RT



// add more elements after second element

iterator.add("Juliet"); // DHJ|RTiterator.add("Nina"); // DHJN|RT

iterator.next(); // DHJNR|T// remove last traversed element

iterator.remove(); // DHJN|T

// print all elements

iterator = staff.listIterator(); while (iterator.hasNext()) System.out.println(iterator.next()); }}



Figure 4Adding a Linkto the Head of aLinked List



Figure 5Removing a Link from the Head of aLinked List



Figure 6Removing a Link from the Middle ofa Linked List



Figure 7Adding a Link to the Middle of aLinked List



Program ListTest2.java

import java.util.NoSuchElementException;

public class ListTest2{ public static void main(String[] args)

{ LinkedList staff = new LinkedList(); staff.addFirst("Tom"); staff.addFirst("Romeo"); staff.addFirst("Harry"); staff.addFirst("Dick"); // | in the comments indicates the iterator position LinkedList.Iterator iterator = staff.listIterator(); // |DHRT iterator.next(); // D|HRT iterator.next(); // DH|RT // add more elements after second element iterator.add("Juliet"); // DHJ|RT iterator.add("Nina"); // DHJN|RT



iterator.next(); // DHJNR|T // remove last traversed element

iterator.remove(); // DHJN|T // print all elements

iterator = staff.listIterator(); while (iterator.hasNext()) System.out.println(iterator.next()); }}

/** A linked list is a sequence of links with efficient element insertion and removal.*/



class LinkedList{ /** Constructs an empty linked list. */ public LinkedList() { first = null; }

/** Returns the first element in the linked list. @return the first element in the linked list */

public Object getFirst() { if (first == null) throw new NoSuchElementException(); return first.data; }



/** Removes the first element in the linked list. @return the removed element*/public Object removeFirst(){ if (first == null) throw new NoSuchElementException(); Object obj = first.data; first = first.next; return obj;}

/** Adds an element to the front of the linked list. @param obj the object to add*/



public void addFirst(Object obj){ Link newLink = new Link(); newLink.data = obj; newLink.next = first; first = newLink;}

/** Returns an iterator for iterating through this list. @return an iterator for iterating through this list*/public Iterator listIterator(){ return new Iterator();}

private Link first;



private class Link{ public Object data; public Link next;}

public class Iterator{ /** Constructs an iterator that points to the front of the linked list. */

public Iterator(){ position = null; previous = null;}/** Moves the iterator past the next element. @return the traversed element*/



public Object next(){ if (position == null) { position = first; return getFirst(); } else { if (position.next == null) throw new NoSuchElementException(); previous = position; // remember for remove position = position.next; return position.data; }}/** Tests whether there is an element after the iterator position. @return true if there is an element after the iterator position*/



public boolean hasNext(){ if (position == null) return first != null; else return position.next != null;}

/** Adds an element before the iterator position and moves the iterator past the inserted element. @param obj the object to add*/public void add(Object obj){ if (position == null) addFirst(obj); else { Link newLink = new Link(); newLink.data = obj; newLink.next = position.next;



position.next = newLink; position = newLink; previous = null; }}

/** Removes the last traversed element. This method may be called only after a call to the next() method.*/public void remove(){ if (position == first) removeFirst();



else { if (previous == null) throw new IllegalStateException(); previous.next = position.next; position = previous; } previous = null; } private Link position; private Link previous; }}



Figure 8A Binary Search Tree



Figure 9A Binary Tree That Is Not a BinarySearch Tree



Figure 10Binary Search Tree after FourInsertions



Figure 11Binary Search Tree after FiveInsertions



Program TreeTest.java

public class TreeTest{ public static void main(String[] args) { Tree staff = new Tree(); staff.insert("Romeo"); staff.insert("Juliet"); staff.insert("Tom"); staff.insert("Dick"); staff.insert("Harry");

staff.print(); }}

/** This class implements a binary search tree whose nodes hold objects that implement the Comparable interface.*/



class Tree{ /** Constructs an empty tree. */ public Tree() { root = null; }

/** Inserts a new node into the tree. @param obj the object to insert */ public void insert(Comparable obj) { Node newNode = new Node(); newNode.data = obj; newNode.left = null; newNode.right = null; if (root == null) root = newNode; else root.insertNode(newNode); }



/** Prints the contents of the tree in sorted order.*/public void print(){ if (root != null) root.printNodes();}

private Node root;



private class Node{ /** Inserts a new node as a descendant of this node. @param newNode the node to insert */ public void insertNode(Node newNode) { if (newNode.data.compareTo(data) < 0) { if (left == null) left = newNode; else left.insertNode(newNode); } else { if (right == null) right = newNode; else right.insertNode(newNode); } }



/** Prints this node and all of its descendants in sorted order. */ public void printNodes() { if (left != null) left.printNodes(); System.out.println(data); if (right != null) right.printNodes(); }

public Comparable data; public Node left; public Node right; }}



Figure 12An Unbalanced Bi-narySearch Tree

chapter 16 data structures 1 ©2000, john wiley & sons, inc. horstmann/java essentials, 2/e...

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