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The source code

/*
 *                 Sun Public License Notice
 * 
 * The contents of this file are subject to the Sun Public License
 * Version 1.0 (the "License"). You may not use this file except in
 * compliance with the License. A copy of the License is available at
 * http://www.sun.com/
 * 
 * The Original Code is NetBeans. The Initial Developer of the Original
 * Code is Sun Microsystems, Inc. Portions Copyright 1997-2000 Sun
 * Microsystems, Inc. All Rights Reserved.
 */

package org.netbeans.modules.form.codestructure;

import java.util.*;

/**
 * @author Tomas Pavek
 */

final class CodeObjectUsage {

    private UsedCodeObject usedObject;
    private java.util.List usageList;

    public CodeObjectUsage(UsedCodeObject usedObject) {
        this.usedObject = usedObject;
    }

    public CodeStructureChange addUsingObject(UsingCodeObject usingObject,
                                              int useType,
                                              Object useCategory,
                                              boolean provideUndoableChange)
    {
        if (useCategory == null)
            throw new IllegalArgumentException();

        if (usageList == null)
            usageList = new LinkedList();

        ObjectUse use = new ObjectUse(usingObject, useType, useCategory);
        usageList.add(use); // [check if the object is not already registered??]

        usingObject.usageRegistered(usedObject);

        return provideUndoableChange ?
               new UsageChange(usedObject, use, true) : null;
    }

    public CodeStructureChange removeUsingObject(UsingCodeObject usingObject,
                                                 boolean provideUndoableChange)
    {
        if (usageList == null)
            return null;

        ObjectUse removed = null;
        Iterator it = usageList.iterator();
        while (it.hasNext()) {
            ObjectUse use = (ObjectUse) it.next();
            if (usingObject == use.usingObject) {
                removed = use;
                it.remove();
            }
        }

        if (removed != null)
            usingObject.usedObjectRemoved(usedObject);

        return provideUndoableChange && removed != null ?
               new UsageChange(usedObject, removed, false) : null;
    }

    public Iterator getUsingObjectsIterator(int useType, Object useCategory) {
        Iterator it = usageList != null ? usageList.iterator() : null;
        return new UsageIterator(it, useType, useCategory);
    }

    public boolean isEmpty() {
        return usageList == null || usageList.size() == 0;
    }

    // -------

    private static class ObjectUse {
        private UsingCodeObject usingObject;
        private int type;
        private Object category;

        ObjectUse(UsingCodeObject usingObject, int useType, Object useCategory) {
            this.usingObject = usingObject;
            this.type = useType;
            this.category = useCategory;
        }

        boolean matches(int type, Object category) {
            if (type != 0 && type != this.type)
                return false;
            if (category == null)
                return true;
            return category.equals(this.category);
        }
    }

    // --------

    private static class UsageChange implements CodeStructureChange {
        private UsedCodeObject usedObject;
        private ObjectUse use;
        private boolean added; // true: added, false: removed

        UsageChange(UsedCodeObject usedObject, ObjectUse use, boolean added) {
            this.usedObject = usedObject;
            this.use = use;
            this.added = added;
        }

        public void undo() {
            if (added)
                usedObject.removeUsingObject(use.usingObject);
            else
                usedObject.addUsingObject(use.usingObject, use.type, use.category);
        }

        public void redo() {
            if (added)
                usedObject.addUsingObject(use.usingObject, use.type, use.category);
            else
                usedObject.removeUsingObject(use.usingObject);
        }
    }

    // --------

    private static class UsageIterator implements Iterator {
        private int useType;
        private Object useCategory;

        private Iterator iterator;
        private Object next;

        public UsageIterator(Iterator iterator,
                             int useType, Object useCategory)
        {
            this.iterator = iterator;
            this.useType = useType;
            this.useCategory = useCategory;
        }

        public boolean hasNext() {
            if (iterator == null)
                return false;
            if (next != null)
                return true;

            while (iterator.hasNext()) {
                ObjectUse use = (ObjectUse) iterator.next();
                if (use.matches(useType, useCategory)) {
                    next = use.usingObject;
                    return true;
                }
            }
            return false;
        }

        public Object next() {
            if (!hasNext())
                throw new NoSuchElementException();

            Object nextObject = next;
            next = null;
            return nextObject;
        }

        public void remove() {
            throw new UnsupportedOperationException();
        }
    }
}
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