CollectionUtilities.java Source code

Introduction

Here is the source code for CollectionUtilities.java

Source

/*
GNU LESSER GENERAL PUBLIC LICENSE
Copyright (C) 2006 The Lobo Project
    
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
    
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Lesser General Public License for more details.
    
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
    
Contact info: lobochief@users.sourceforge.net
*/
/*
 * Created on Jun 9, 2005
 */

import java.util.*;

/**
 * @author J. H. S.
 */
class CollectionUtilities {
    /**
     * 
     */
    private CollectionUtilities() {
        super();
    }

    public static Enumeration getIteratorEnumeration(final Iterator i) {
        return new Enumeration() {
            public boolean hasMoreElements() {
                return i.hasNext();
            }

            public Object nextElement() {
                return i.next();
            }
        };
    }

    public static Iterator iteratorUnion(final Iterator[] iterators) {
        return new Iterator() {
            private int iteratorIndex = 0;
            private Iterator current = iterators.length > 0 ? iterators[0] : null;

            public boolean hasNext() {
                for (;;) {
                    if (current == null) {
                        return false;
                    }
                    if (current.hasNext()) {
                        return true;
                    }
                    iteratorIndex++;
                    current = iteratorIndex >= iterators.length ? null : iterators[iteratorIndex];
                }
            }

            public Object next() {
                for (;;) {
                    if (this.current == null) {
                        throw new NoSuchElementException();
                    }
                    try {
                        return this.current.next();
                    } catch (NoSuchElementException nse) {
                        this.iteratorIndex++;
                        this.current = this.iteratorIndex >= iterators.length ? null
                                : iterators[this.iteratorIndex];
                    }
                }
            }

            public void remove() {
                if (this.current == null) {
                    throw new NoSuchElementException();
                }
                this.current.remove();
            }
        };
    }

    public static Collection reverse(Collection collection) {
        LinkedList newCollection = new LinkedList();
        Iterator i = collection.iterator();
        while (i.hasNext()) {
            newCollection.addFirst(i.next());
        }
        return newCollection;
    }

    public static Iterator singletonIterator(final Object item) {
        return new Iterator() {
            private boolean gotItem = false;

            public boolean hasNext() {
                return !this.gotItem;
            }

            public Object next() {
                if (this.gotItem) {
                    throw new NoSuchElementException();
                }
                this.gotItem = true;
                return item;
            }

            public void remove() {
                if (!this.gotItem) {
                    this.gotItem = true;
                } else {
                    throw new NoSuchElementException();
                }
            }
        };
    }
}