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
 * specific language governing permissions and limitations under the
 * License.  When distributing the software, include this License Header
 * Notice in each file and include the License file at
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 * particular file as subject to the "Classpath" exception as provided
 * by Sun in the GPL Version 2 section of the License file that
 * accompanied this code. If applicable, add the following below the
 * License Header, with the fields enclosed by brackets [] replaced by
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 * "Portions Copyrighted [year] [name of copyright owner]"
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 * Contributor(s):
 *
 * The Original Software is NetBeans. The Initial Developer of the Original
 * Software is Sun Microsystems, Inc. Portions Copyright 1997-2006 Sun
 * Microsystems, Inc. All Rights Reserved.
 *
 * If you wish your version of this file to be governed by only the CDDL
 * or only the GPL Version 2, indicate your decision by adding
 * "[Contributor] elects to include this software in this distribution
 * under the [CDDL or GPL Version 2] license." If you do not indicate a
 * single choice of license, a recipient has the option to distribute
 * 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
 * Version 2 license, then the option applies only if the new code is
 * made subject to such option by the copyright holder.
 */

import java.io.Serializable;
import java.util.AbstractSet;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Set;

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

public class Utils {
    /**
     * Create a typesafe view over an underlying raw set.
     * Mutations affect the underlying set (this is not a copy).
     * {@link Set#clear} will make the view empty but may not clear the underlying set.
     * You may add elements only of the requested type.
     * {@link Set#contains} also performs a type check and will throw {@link ClassCastException}
     * for an illegal argument.
     * The view is serializable if the underlying set is.
     * @param rawSet an unchecked set
     * @param type the desired element type
     * @param strict if false, elements in the underlying set which are not null and which are not assignable
     *               to the requested type are omitted from the view;
     *               if true, a {@link ClassCastException} may arise during some set operation
     * @return a view over the raw set guaranteed to match the specified type
     */
    public static <E> Set<E> checkedSetByFilter(Set rawSet, Class<E> type, boolean strict) {
        return new CheckedSet<E>(rawSet, type, strict);
    }

    private static final class CheckedSet<E> extends AbstractSet<E> implements Serializable {

        private static final long serialVersionUID = 1L;

        private final Set rawSet;
        private final Class<E> type;
        private final boolean strict;

        public CheckedSet(Set rawSet, Class<E> type, boolean strict) {
            this.rawSet = rawSet;
            this.type = type;
            this.strict = strict;
        }

        private boolean acceptEntry(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;
            }
        }

        @Override
        public Iterator<E> iterator() {
            return new CheckedIterator<E>(rawSet.iterator()) {
                @Override
                protected boolean accept(Object o) {
                    return acceptEntry(o);
                }
            };
        }

        @Override
        public int size() {
            int c = 0;
            Iterator it = rawSet.iterator();
            while (it.hasNext()) {
                if (acceptEntry(it.next())) {
                    c++;
                }
            }
            return c;
        }

        @Override
        @SuppressWarnings("unchecked") // complains about usage of raw set
        public boolean add(E o) {
            return rawSet.add(type.cast(o));
        }

        @Override
        public boolean contains(Object o) {
            return rawSet.contains(type.cast(o));
        }

    }

}

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();
    }

}