collections.java

gcc的组建

      return equals(key, k);
    }

    /**
     * Single entry.
     *
     * @param value The value to look for.
     * @return <code>true</code> if the value is the same as the one used by
     *         this map.
     */
    public boolean containsValue(Object value)
    {
      return equals(value, v);
    }

    /**
     * Single entry.
     *
     * @param key The key of the value to be retrieved.
     * @return The singleton value if the key is the same as the
     *         singleton key, null otherwise.
     */
    public Object get(Object key)
    {
      return equals(key, k) ? v : null;
    }

    /**
     * Calculate the hashcode directly.
     *
     * @return The hashcode computed from the singleton key
     *         and the singleton value.
     */
    public int hashCode()
    {
      return hashCode(k) ^ hashCode(v);
    }

    /**
     * Return the keyset.
     *
     * @return A singleton containing the key.
     */
    public Set keySet()
    {
      if (keys == null)
        keys = singleton(k);
      return keys;
    }

    /**
     * The size: always 1!
     *
     * @return 1.
     */
    public int size()
    {
      return 1;
    }

    /**
     * Return the values. Technically, a singleton, while more specific than
     * a general Collection, will work. Besides, that's what the JDK uses!
     *
     * @return A singleton containing the value.
     */
    public Collection values()
    {
      if (values == null)
        values = singleton(v);
      return values;
    }

    /**
     * Obvious string.
     *
     * @return A string containing the string representations of the key
     *         and its associated value.
     */
    public String toString()
    {
      return "{" + k + "=" + v + "}";
    }
  } // class SingletonMap

  /**
   * Sort a list according to the natural ordering of its elements. The list
   * must be modifiable, but can be of fixed size. The sort algorithm is
   * precisely that used by Arrays.sort(Object[]), which offers guaranteed
   * nlog(n) performance. This implementation dumps the list into an array,
   * sorts the array, and then iterates over the list setting each element from
   * the array.
   *
   * @param l the List to sort
   * @throws ClassCastException if some items are not mutually comparable
   * @throws UnsupportedOperationException if the List is not modifiable
   * @throws NullPointerException if some element is null
   * @see Arrays#sort(Object[])
   */
  public static void sort(List l)
  {
    sort(l, null);
  }

  /**
   * Sort a list according to a specified Comparator. The list must be
   * modifiable, but can be of fixed size. The sort algorithm is precisely that
   * used by Arrays.sort(Object[], Comparator), which offers guaranteed
   * nlog(n) performance. This implementation dumps the list into an array,
   * sorts the array, and then iterates over the list setting each element from
   * the array.
   *
   * @param l the List to sort
   * @param c the Comparator specifying the ordering for the elements, or
   *        null for natural ordering
   * @throws ClassCastException if c will not compare some pair of items
   * @throws UnsupportedOperationException if the List is not modifiable
   * @throws NullPointerException if null is compared by natural ordering
   *        (only possible when c is null)
   * @see Arrays#sort(Object[], Comparator)
   */
  public static void sort(List l, Comparator c)
  {
    Object[] a = l.toArray();
    Arrays.sort(a, c);
    ListIterator i = l.listIterator();
    for (int pos = 0, alen = a.length;  pos < alen;  pos++)
      {
        i.next();
        i.set(a[pos]);
      }
  }

  /**
   * Swaps the elements at the specified positions within the list. Equal
   * positions have no effect.
   *
   * @param l the list to work on
   * @param i the first index to swap
   * @param j the second index
   * @throws UnsupportedOperationException if list.set is not supported
   * @throws IndexOutOfBoundsException if either i or j is &lt; 0 or &gt;=
   *         list.size()
   * @since 1.4
   */
  public static void swap(List l, int i, int j)
  {
    l.set(i, l.set(j, l.get(i)));
  }


  /**
   * Returns a synchronized (thread-safe) collection wrapper backed by the
   * given collection. Notice that element access through the iterators
   * is thread-safe, but if the collection can be structurally modified
   * (adding or removing elements) then you should synchronize around the
   * iteration to avoid non-deterministic behavior:<br>
   * <pre>
   * Collection c = Collections.synchronizedCollection(new Collection(...));
   * ...
   * synchronized (c)
   *   {
   *     Iterator i = c.iterator();
   *     while (i.hasNext())
   *       foo(i.next());
   *   }
   * </pre><p>
   *
   * Since the collection might be a List or a Set, and those have incompatible
   * equals and hashCode requirements, this relies on Object's implementation
   * rather than passing those calls on to the wrapped collection. The returned
   * Collection implements Serializable, but can only be serialized if
   * the collection it wraps is likewise Serializable.
   *
   * @param c the collection to wrap
   * @return a synchronized view of the collection
   * @see Serializable
   */
  public static Collection synchronizedCollection(Collection c)
  {
    return new SynchronizedCollection(c);
  }

  /**
   * The implementation of {@link #synchronizedCollection(Collection)}. This
   * class name is required for compatibility with Sun's JDK serializability.
   * Package visible, so that collections such as the one for
   * Hashtable.values() can specify which object to synchronize on.
   *
   * @author Eric Blake ([e-mail])
   */
  static class SynchronizedCollection
    implements Collection, Serializable
  {
    /**
     * Compatible with JDK 1.4.
     */
    private static final long serialVersionUID = 3053995032091335093L;

    /**
     * The wrapped collection. Package visible for use by subclasses.
     * @serial the real collection
     */
    final Collection c;

    /**
     * The object to synchronize on.  When an instance is created via public
     * methods, it will be this; but other uses like SynchronizedMap.values()
     * must specify another mutex. Package visible for use by subclasses.
     * @serial the lock
     */
    final Object mutex;

    /**
     * Wrap a given collection.
     * @param c the collection to wrap
     * @throws NullPointerException if c is null
     */
    SynchronizedCollection(Collection c)
    {
      this.c = c;
      mutex = this;
      if (c == null)
        throw new NullPointerException();
    }

    /**
     * Called only by trusted code to specify the mutex as well as the
     * collection.
     * @param sync the mutex
     * @param c the collection
     */
    SynchronizedCollection(Object sync, Collection c)
    {
      this.c = c;
      mutex = sync;
    }

    /**
     * Adds the object to the underlying collection, first
     * obtaining a lock on the mutex.
     *
     * @param o The object to add.
     * @return <code>true</code> if the collection was modified as a result
     *         of this action.
     * @throws UnsupportedOperationException if this collection does not
     *         support the add operation.
     * @throws ClassCastException if o cannot be added to this collection due
     *         to its type.
     * @throws NullPointerException if o is null and this collection doesn't
     *         support the addition of null values.
     * @throws IllegalArgumentException if o cannot be added to this
     *         collection for some other reason.
     */
    public boolean add(Object o)
    {
      synchronized (mutex)
        {
          return c.add(o);
        }
    }

    /**
     * Adds the objects in col to the underlying collection, first
     * obtaining a lock on the mutex.
     *
     * @param col The collection to take the new objects from.
     * @return <code>true</code> if the collection was modified as a result
     *          of this action.
     * @throws UnsupportedOperationException if this collection does not
     *         support the addAll operation.
     * @throws ClassCastException if some element of col cannot be added to this
     *         collection due to its type.
     * @throws NullPointerException if some element of col is null and this
     *         collection does not support the addition of null values.
     * @throws NullPointerException if col itself is null.
     * @throws IllegalArgumentException if some element of col cannot be added
     *         to this collection for some other reason.
     */
    public boolean addAll(Collection col)
    {
      synchronized (mutex)
        {
          return c.addAll(col);
        }
    }

    /**
     * Removes all objects from the underlying collection,
     * first obtaining a lock on the mutex.
     *
     * @throws UnsupportedOperationException if this collection does not
     *         support the clear operation.
     */
    public void clear()
    {
      synchronized (mutex)
        {
          c.clear();
        }
    }

    /**
     * Checks for the existence of o within the underlying
     * collection, first obtaining a lock on the mutex.
     *
     * @param o the element to look for.
     * @return <code>true</code> if this collection contains at least one
     *         element e such that <code>o == null ? e == null : o.equals(e)</code>.
     * @throws ClassCastException if the type of o is not a valid type for this
     *         collection.
     * @throws NullPointerException if o is null and this collection doesn't
     *         support null values.
     */
    public boolean contains(Object o)
    {
      synchronized (mutex)
        {
          return c.contains(o);
        }
    }

    /**
     * Checks for the existence of each object in cl
     * within the underlying collection, first obtaining
     * a lock on the mutex.
     *
     * @param c1 the collection to test for.
     * @return <code>true</code> if for every element o in c, contains(o)
     *         would return <code>true</code>.
     * @throws ClassCastException if the type of any element in cl is not a valid
     *         type for this collection.
     * @throws NullPointerException if some element of cl is null and this
     *         collection does not support null values.
     * @throws NullPointerException if cl itself is null.
     */
    public boolean containsAll(Collection c1)
    {
      synchronized (mutex)
        {
          return c.containsAll(c1);
        }
    }

    /**
     * Returns <code>true</code> if there are no objects in the underlying
     * collection.  A lock on the mutex is obtained before the
     * check is performed.
     *
     * @return <code>true</code> if this collection contains no elements.
     */
    public boolean isEmpty()
    {
      synchronized (mutex)
        {
          return c.isEmpty();
        }
    }

    /**
     * Returns a synchronized iterator wrapper around the underlying
     * collection's iterator.  A lock on the mutex is obtained before
     * retrieving the collection's iterator.
     *
     * @return An iterator over the elements in the underlying collection,
     *         which returns each element in any order.
     */
    public Iterator iterator()
    {
      synchronized (mutex)
        {
          return new SynchronizedIterator(mutex, c.iterator());
        }
    }

    /**
     * Removes the specified object from the underlying collection,
     * first obtaining a lock on the mutex.
     *
     * @param o The object to remove.
     * @return <code>true</code> if the collection changed as a result of this call, that is,
     *         if the collection contained at least one occurrence of o.
     * @throws UnsupportedOperationException if this collection does not
     *         support the remove operation.
     * @throws ClassCastException if the type of o is not a valid type
     *         for this collection.
     * @throws NullPointerException if o is null and the collection doesn't
     *         support null values.
     */
    public boolean remove(Object o)
    {
      synchronized (mutex)
        {
          return c.remove(o);
        }
    }

    /**
     * Removes all elements, e, of the underlying
     * collection for which <code>col.contains(e)</code>
     * returns <code>true</code>.  A lock on the mutex is obtained
     * before the operation proceeds.
     *
     * @param col The collection of objects to be removed.
     * @return <code>true</code> if this collection was modified as a result of this call.
     * @throws UnsupportedOperationException if this collection does not
     *   support the removeAll operation.
     * @throws ClassCastException if the type of any element in c is not a valid
     *   type for this collection.
     * @throws NullPointerException if some element of c is null and this
     *   collection does not support removing null values.
     * @throws NullPointerException if c itself is null.
     */
    public boolean removeAll(Collection col)
    {
      synchronized (mutex)
        {
          return c.removeAll(col);
        }
    }

    /**
     * Retains all elements, e, of the underlying
     * collection for which <code>col.contains(e)</code>
     * returns <code>true</code>.  That is, every element that doesn't
     * exist in col is removed.  A lock on the mutex is obtained
     * before the operation proceeds.
     *
     * @param col The collection of objects to be removed.
     * @return <code>true</code> if this collection was modified as a result of this call.
     * @throws UnsupportedOperationException if this collection does not
     *   support the removeAll operation.
     * @throws ClassCastException if the type of any element in c is not a valid
     *   type for this collection.
     * @throws NullPointerException if some element of c is null and this
     *   collection does not support removing null values.
     * @throws NullPointerException if c itself is null.
     */
    public boolean retainAll(Collection col)
    {
      synchronized (mutex)
        {
          return c.retainAll(col);
        }
    }

    /**
     * Retrieves the size of the underlying collection.
     * A lock on the mutex is obtained before the collection
     * is accessed.
     *
     * @return Th