ActiveX Programming Unleashed CD/AXU.iso/jgl_1_1/jgl_1_1.exe/src/OrderedSet.java

Java Source | 1996-09-10 | 15.8 KB | 484 lines

// Copyright(c) 1996 ObjectSpace, Inc.
// Portions Copyright(c) 1995, 1996 Hewlett-Packard Company.

package jgl;

import java.util.Enumeration;

/**
 * A OrderedSet is a container that is optimized for fast associative lookup. Items are
 * matched using equals(). When an item is inserted into a OrderedSet, it is stored in a
 * data structure that allows the item to be found very quickly. Within the data
 * structure, the items are ordered according to a comparator object. By default, the
 * comparator is a HashComparator that orders objects based on their hash value.
 * The OrderedSet class supports the full range of generic set algorithms such as
 * union() and intersection() in a user-friendly manner.  Duplicates are not allowed
 * by default.
 * <p>
 * OrderedSets are useful when fast associate lookup is important and when index-based
 * lookup is unnecessary.
 * <p>
 * Strictly speaking, there is no reason why null is not a valid entry. However, most
 * comparators (including the default HashComparator) will fail and throw an exception
 * if you attempt to add a null entry because they cast the entry to a class and then
 * activate one of its methods. It is perfectly possible to hand-craft a comparator
 * that will accept null as a valid key.
 * <p>
 * There are many different approaches that could be used to implementing an associative
 * container. For example, most of the older libraries used a hashing scheme for
 * positioning and retrieving items. This implementation use a data structure called a
 * red-black tree. A red-black tree is a binary search tree that uses an extra field in
 * every node to store the node's color. Red-black trees constrain the way that nodes may
 * be colored in such a way that the tree remains reasonably balanced. This property is
 * important for ensuring a good overall performance - red-black trees guarantee that the
 * worst case performance for the most common dynamic set operations is O(log N). One
 * conseqence of using a binary tree for storage of data is that the items remain in a
 * sorted order. This allows SGL users to iterate through an associative container and
 * access its elements in a sequenced manner.
 * <p>
 * Insertion does not affect iterators or references.
 * <p>
 * Removal only invalidates the iterators and references to the removed elements.
 * <p>
 * @see jgl.OrderedMultiset
 * @see jgl.BinaryPredicate
 * @see jgl.SetOperations
 * @see jgl.examples.OrderedSetExamples
 * @version 1.1
 * @author ObjectSpace, Inc.
 */

public class OrderedSet implements Set
  {
  Tree myTree;

  /**
   * Construct myself to be an empty OrderedSet that orders elements based on
   * their hash value and does not allow duplicates.
   */
  public OrderedSet()
    {
    myTree = new Tree( false, false, this );
    }

  /**
   * Construct myself to be an empty OrderedSet that orders elements based on
   * their hash value and conditionally allows duplicates.
   * @param allowDuplicates true if duplicates are allowed.
   */
  public OrderedSet( boolean allowDuplicates )
    {
    myTree = new Tree( false, allowDuplicates, this );
    }

  /**
   * Construct myself to be an empty OrderedSet that orders elements using
   * a specified binary predicate and does not allow duplicates.
   * @param comparator The predicate for ordering objects.
   */
  public OrderedSet( BinaryPredicate comparator )
    {
    myTree = new Tree( false, false, comparator, this );
    }

  /**
   * Construct myself to be an empty OrderedSet that orders elements using
   * a specified binary predicate and conditionally allows duplicates.
   * @param comparator The predicate for ordering objects.
   * @param allowDuplicates true if duplicates are allowed.
   */
  public OrderedSet( BinaryPredicate comparator, boolean allowDuplicates )
    {
    myTree = new Tree( false, allowDuplicates, comparator, this );
    }

  /**
   * Construct myself to be a shallow copy of an existing OrderedSet.
   * @param set The OrderedSet to copy.
   */
  public OrderedSet( OrderedSet set )
    {
    myTree = new Tree( set.myTree );
    }

  /**
   * Return true if duplicates are allowed.
   */
  public boolean allowsDuplicates()
    {
    return myTree.myInsertAlways;
    }

  /**
   * Return a shallow copy of myself.
   */
  public synchronized Object clone()
    {
    return new OrderedSet( this );
    }

  /**
   * Become a shallow copy of an existing OrderedSet.
   * @param set The OrderedSet that I shall become a shallow copy of.
   */
  public synchronized void copy( OrderedSet set )
    {
    myTree.copy( set.myTree );
    }

  /**
   * Return a string that describes me.
   */
  public synchronized String toString()
    {
    return Printing.toString( this, "OrderedSet" );
    }

  /**
   * Return an Enumeration of my components.
   */
  public synchronized Enumeration elements()
    {
    return myTree.beginSet();
    }

  /**
   * Return an iterator positioned at my first item.
   */
  public synchronized ForwardIterator start()
    {
    return myTree.beginSet();
    }

  /**
   * Return an iterator positioned immediately afer my last item.
   */
  public synchronized ForwardIterator finish()
    {
    return myTree.endSet();
    }

  /**
   * Return an iterator positioned at my first item.
   */
  public synchronized OrderedSetIterator begin()
    {
    return myTree.beginSet();
    }

  /**
   * Return an iterator positioned immediately after my last item.
   */
  public synchronized OrderedSetIterator end()
    {
    return myTree.endSet();
    }

  /**
   * Return true if I contain no entries.
   */
  public boolean isEmpty()
    {
    return myTree.size == 0;
    }

  /**
   * Return the number of entries that I contain.
   */
  public int size()
    {
    return myTree.size;
    }

  /**
   * Return the maximum number of entries that I can contain.
   */
  public int maxSize()
    {
    return myTree.maxSize();
    }

  /**
   * Return true if I'm equal to another object.
   * @param object The object to compare myself against.
   */
  public boolean equals( Object object )
    {
    return object instanceof OrderedSet && equals( (OrderedSet) object );
    }

  /**
   * Return true if I contain the same items in the same order as
   * another OrderedSet. Use equals() to compare the individual elements.
   * @param set The OrderedSet to compare myself against.
   */
  public synchronized boolean equals( OrderedSet set )
    {
    return Comparing.equal( this, set );
    }

  /**
   * Return my hash code for support of hashing containers
   */
  public int hashCode()
    {
    return Hashing.orderedHash( this );
    }

  /**
   * Swap my contents with another OrderedSet.
   * @param set The OrderedSet that I will swap my contents with.
   */
  public synchronized void swap( OrderedSet set )
    {
    Tree tmp = myTree;
    myTree = set.myTree;
    set.myTree = tmp;
    }

  /**
   * Remove all of my elements.
   */
  public synchronized void clear()
    {
    myTree.clear();
    }

  /**
   * Remove all objects that match the given object.
   * @param object The object to match for removals
   * @return Return The first object removed or null if none exists.
   */
  public synchronized Object remove( Object object )
    {
    return myTree.remove( object );
    }

  /**
   * Remove the element at a particular position.
   * @param e An Enumeration positioned at the element to remove.
   * @exception IllegalArgumentException if the Enumeration isn't a
   * OrderedSetIterator for this OrderedSet object.
   * @return The object that was removed or null if none
   */
  public synchronized Object remove( Enumeration e )
    {
    if( ! (e instanceof OrderedSetIterator) )
      throw new IllegalArgumentException( "Enumeration not a OrderedSetIterator" );

    if( ((OrderedSetIterator)e).myOrderedSet != this )
      throw new IllegalArgumentException( "Enumeration not for this OrderedSet" );

    TreeNode node = myTree.remove( ((OrderedSetIterator)e).myNode );
    return ( node == null ? null : node.object );
    }

  /**
   * Remove the elements within a specified range.
   * @param first An Enumeration positioned at the first element to remove.
   * @param last An Enumeration positioned immediately after the last element to remove.
   * @exception IllegalArgumentException is the Enumeration isn't a
   * OrderedSetIterator for this OrderedSet object.
   */
  public synchronized void remove( Enumeration first, Enumeration last )
    {
    if( ( ! (first instanceof OrderedSetIterator) ) ||
        ( ! (last instanceof OrderedSetIterator) ) )
      throw new IllegalArgumentException( "Enumeration not a OrderedSetIterator" );

    if( ( ((OrderedSetIterator)first).myOrderedSet != this ) ||
        ( ((OrderedSetIterator)last).myOrderedSet != this ) )
      throw new IllegalArgumentException( "Enumeration not for this OrderedSet" );

    myTree.remove( ((OrderedSetIterator)first).myNode, ((OrderedSetIterator)last).myNode );
    }

  /**
   * Find an object and return its position. If the object
   * is not found, return end().
   * @param object The object to locate.
   */
  public synchronized OrderedSetIterator find( Object object )
    {
    return new OrderedSetIterator( myTree, myTree.find( object ), this );
    }

  /**
   * Return the number of items that match a particular object.
   * @param object The object to match against.
   */
  public synchronized int count( Object object )
    {
    return myTree.count( object );
    }

  /**
   * Return an iterator positioned at the first location that a
   * particular object could be inserted without violating the ordering
   * criteria. If no such location is found, return an iterator
   * positioned at end().
   * @param object The object in question.
   */
  public synchronized OrderedSetIterator lowerBound( Object object )
    {
    return new OrderedSetIterator( myTree, myTree.lowerBound( object ), this );
    }

  /**
   * Return an iterator positioned at the last location that
   * a particular object could be inserted without violating the ordering
   * criteria. If no such location is found, return an iterator
   * positioned at end().
   * @param object The object in question.
   */
  public synchronized OrderedSetIterator upperBound( Object object )
    {
    return new OrderedSetIterator( myTree, myTree.upperBound( object ), this );
    }

  /**
   * Return my comparator.
   */
  public BinaryPredicate getComparator()
    {
    return myTree.myComparator;
    }

  /**
   * If the object doesn't exist or duplicates are allowed, add the object and return null,
   * otherwise don't modify the set and return the matching object.
   * @param object The object to be added.
   * @exception NullPointerException If the value of the object is equal to null.
   */
  public synchronized Object add( Object object )
    {
    if( object == null )
      throw new NullPointerException();

    InsertResult result = myTree.insert( object );
    return result.ok ? null : result.node.object;
    }

  /**
   * Return the first object that matches the given object, or null if no match exists.
   * @param object The object to match against.
   */
  public synchronized Object get( Object object )
    {
    TreeNode node = myTree.find( object );
    return node.object.equals( object ) ? node.object : null;
    }

  /**
   * If the object doesn't exist, add the object and return null, otherwise replace the
   * first object that matches and return the old object.
   * @param object The object to add.
   * @exception NullPointerException If the value of the object is equal to null.
   */
  public synchronized Object put( Object object )
    {
    if( object == null )
      throw new NullPointerException();

    InsertResult result = myTree.put( object );
    return result.ok ? null : result.node.object;
    }

  /**
   * Return a new OrderedSet that contains all of my elements and all of the elements in
   * a specified OrderedSet.
   * @param set The OrderedSet to union myself with.
   * @exception jgl.InvalidOperationException if set is in multi-mode.
   */
  public synchronized OrderedSet union( OrderedSet set )
    {
    if( myTree.myInsertAlways || set.myTree.myInsertAlways )
      throw new InvalidOperationException( "union operation invalid on multisets" );

    OrderedSet result = new OrderedSet( getComparator(), allowsDuplicates() );
    SetOperations.setUnion( this, set, new InsertIterator( result ), getComparator() );
    return result;
    }

  /**
   * Return a new OrderedSet that contains the elements that are both in me and in
   * a specified set.
   * @param set The OrderedSet to intersect myself with.
   */
  public synchronized OrderedSet intersection( OrderedSet set )
    {
    if( myTree.myInsertAlways || set.myTree.myInsertAlways )
      throw new InvalidOperationException( "intersection operation invalid on multisets" );

    OrderedSet result = new OrderedSet( getComparator(), allowsDuplicates() );
    SetOperations.setIntersection( this, set, new InsertIterator( result ), getComparator() );
    return result;
    }

  /**
   * Return a new OrderedSet that contains the elements that are in me but not in a
   * specified set.
   * @param set The OrderedSet to difference myself with.
   */
  public synchronized OrderedSet difference( OrderedSet set )
    {
    if( myTree.myInsertAlways || set.myTree.myInsertAlways )
      throw new InvalidOperationException( "difference operation invalid on multisets" );

    OrderedSet result = new OrderedSet( getComparator(), allowsDuplicates() );
    SetOperations.setDifference( this, set, new InsertIterator( result ), getComparator() );
    return result;
    }

  /**
   * Return a new OrderedSet that contains the elements that are either in me or in
   * a specified OrderedSet, but not both.
   * @param set The OrderedSet to symmetric difference myself with.
   */
  public synchronized OrderedSet symmetricDifference( OrderedSet set )
    {
    if( myTree.myInsertAlways || set.myTree.myInsertAlways )
      throw new InvalidOperationException( "symmetricDifference operation invalid on multisets" );

    OrderedSet result = new OrderedSet( getComparator(), allowsDuplicates() );
    SetOperations.setSymmetricDifference( this, set, new InsertIterator( result ), getComparator() );
    return result;
    }

  /**
   * Return true if every element in me is also in a specified OrderedSet.
   * @param set The OrderedSet to test against.
   */
  public synchronized boolean subsetOf( OrderedSet set )
    {
    if( myTree.myInsertAlways || set.myTree.myInsertAlways )
      throw new InvalidOperationException( "subsetOf operation invalid on multisets" );

    return SetOperations.includes( set, this, getComparator() );
    }

  /**
   * Return true if every element in me is also in a specified OrderedSet and I'm smaller
   * than the specified OrderedSet.
   * @param set The OrderedSet to test against.
   */
  public synchronized boolean properSubsetOf( OrderedSet set )
    {
    if( myTree.myInsertAlways || set.myTree.myInsertAlways )
      throw new InvalidOperationException( "properSubsetOf operation invalid on multisets" );

    return (size() < set.size()) && subsetOf( set );
    }

  /**
   * Return a range whose first element is equal to
   * lowerBound() and whose second element is equal to upperBound().
   * @param object The object whose bounds are to be found.
   */
  public synchronized Range equalRange( Object object )
    {
    return new Range( lowerBound( object ), upperBound( object ) );
    }
  }