Utils.java Source code

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Here is the source code for Utils.java

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/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved.
 *
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common
 * Development and Distribution License("CDDL") (collectively, the
 * "License"). You may not use this file except in compliance with the
 * License. You can obtain a copy of the License at
 * http://www.netbeans.org/cddl-gplv2.html
 * or nbbuild/licenses/CDDL-GPL-2-CP. See the License for the
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 * particular file as subject to the "Classpath" exception as provided
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 * The Original Software is NetBeans. The Initial Developer of the Original
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 * If you wish your version of this file to be governed by only the CDDL
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 * your version of this file under either the CDDL, the GPL Version 2 or
 * to extend the choice of license to its licensees as provided above.
 * However, if you add GPL Version 2 code and therefore, elected the GPL
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 */

import java.util.Iterator;
import java.util.NoSuchElementException;

/**
 * @since 4.37
 * @author Jaroslav Tulach
 */

public class Utils {
    /**
     * Create a typesafe filter of an unchecked iterator. {@link Iterator#remove}
     * will work if it does in the unchecked iterator.
     * 
     * @param rawIterator
     *          an unchecked iterator
     * @param type
     *          the desired enumeration type
     * @param strict
     *          if false, elements which are not null but not assignable to the
     *          requested type are omitted; if true, {@link ClassCastException}
     *          may be thrown from an iterator operation
     * @return an iterator guaranteed to contain only objects of the requested
     *         type (or null)
     */
    public static <E> Iterator<E> checkedIteratorByFilter(Iterator rawIterator, final Class<E> type,
            final boolean strict) {
        return new CheckedIterator<E>(rawIterator) {
            protected boolean accept(Object o) {
                if (o == null) {
                    return true;
                } else if (type.isInstance(o)) {
                    return true;
                } else if (strict) {
                    throw new ClassCastException(o + " was not a " + type.getName()); // NOI18N
                } else {
                    return false;
                }
            }
        };
    }

}

abstract class CheckedIterator<E> implements Iterator<E> {

    static final Object WAITING = new Object();

    private final Iterator it;

    private Object next = WAITING;

    public CheckedIterator(Iterator it) {
        this.it = it;
    }

    protected abstract boolean accept(Object o);

    public boolean hasNext() {
        if (next != WAITING) {
            return true;
        }
        while (it.hasNext()) {
            next = it.next();
            if (accept(next)) {
                return true;
            }
        }
        next = WAITING;
        return false;
    }

    public E next() {
        if (next == WAITING && !hasNext()) {
            throw new NoSuchElementException();
        }
        assert next != WAITING;
        @SuppressWarnings("unchecked")
        // type-checking is done by accept()
        E x = (E) next;
        next = WAITING;
        return x;
    }

    public void remove() {
        it.remove();
    }

}