/*

 * Copyright (c) 1996, 2000, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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 General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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/*

 * (C) Copyright Taligent, Inc. 1996, 1997 - All Rights Reserved

 * (C) Copyright IBM Corp. 1996 - 1998 - All Rights Reserved

 *

 * The original version of this source code and documentation

 * is copyrighted and owned by Taligent, Inc., a wholly-owned

 * subsidiary of IBM. These materials are provided under terms

 * of a License Agreement between Taligent and Sun. This technology

 * is protected by multiple US and International patents.

 *

 * This notice and attribution to Taligent may not be removed.

 * Taligent is a registered trademark of Taligent, Inc.

 *

 */

package java.text;

/**

 * This interface defines a protocol for bidirectional iteration over text.

 * The iterator iterates over a bounded sequence of characters.  Characters

 * are indexed with values beginning with the value returned by getBeginIndex() and

 * continuing through the value returned by getEndIndex()-1.

 * <p>

 * Iterators maintain a current character index, whose valid range is from

 * getBeginIndex() to getEndIndex(); the value getEndIndex() is included to allow

 * handling of zero-length text ranges and for historical reasons.

 * The current index can be retrieved by calling getIndex() and set directly

 * by calling setIndex(), first(), and last().

 * <p>

 * The methods previous() and next() are used for iteration. They return DONE if

 * they would move outside the range from getBeginIndex() to getEndIndex() -1,

 * signaling that the iterator has reached the end of the sequence. DONE is

 * also returned by other methods to indicate that the current index is

 * outside this range.

 *

 * <P>Examples:<P>

 *

 * Traverse the text from start to finish

 * public void traverseForward(CharacterIterator iter) {

 *     for(char c = iter.first(); c != CharacterIterator.DONE; c = iter.next()) {

 *         processChar(c);

 *     }

 * }

 *

 * Traverse the text backwards, from end to start

 * public void traverseBackward(CharacterIterator iter) {

 *     for(char c = iter.last(); c != CharacterIterator.DONE; c = iter.previous()) {

 *         processChar(c);

 *     }

 * }

 *

 * Traverse both forward and backward from a given position in the text.

 * Calls to notBoundary() in this example represents some

 * additional stopping criteria.

 * public void traverseOut(CharacterIterator iter, int pos) {

 *     for (char c = iter.setIndex(pos);

 *              c != CharacterIterator.DONE && notBoundary(c);

 *              c = iter.next()) {

 *     }

 *     int end = iter.getIndex();

 *     for (char c = iter.setIndex(pos);

 *             c != CharacterIterator.DONE && notBoundary(c);

 *             c = iter.previous()) {

 *     }

 *     int start = iter.getIndex();

 *     processSection(start, end);

 * }

 *

 * @see StringCharacterIterator

 * @see AttributedCharacterIterator

 */

public interface CharacterIterator extends Cloneable

{

    /**

     * Constant that is returned when the iterator has reached either the end

     * or the beginning of the text. The value is '\\uFFFF', the "not a

     * character" value which should not occur in any valid Unicode string.

     */

    public static final char DONE = '\uFFFF';

    /**

     * Sets the position to getBeginIndex() and returns the character at that

     * position.

     * @return the first character in the text, or DONE if the text is empty

     * @see #getBeginIndex()

     */

    public char first();

    /**

     * Sets the position to getEndIndex()-1 (getEndIndex() if the text is empty)

     * and returns the character at that position.

     * @return the last character in the text, or DONE if the text is empty

     * @see #getEndIndex()

     */

    public char last();

    /**

     * Gets the character at the current position (as returned by getIndex()).

     * @return the character at the current position or DONE if the current

     * position is off the end of the text.

     * @see #getIndex()

     */

    public char current();

    /**

     * Increments the iterator's index by one and returns the character

     * at the new index.  If the resulting index is greater or equal

     * to getEndIndex(), the current index is reset to getEndIndex() and

     * a value of DONE is returned.

     * @return the character at the new position or DONE if the new

     * position is off the end of the text range.

     */

    public char next();

    /**

     * Decrements the iterator's index by one and returns the character

     * at the new index. If the current index is getBeginIndex(), the index

     * remains at getBeginIndex() and a value of DONE is returned.

     * @return the character at the new position or DONE if the current

     * position is equal to getBeginIndex().

     */

    public char previous();

    /**

     * Sets the position to the specified position in the text and returns that

     * character.

     * @param position the position within the text.  Valid values range from

     * getBeginIndex() to getEndIndex().  An IllegalArgumentException is thrown

     * if an invalid value is supplied.

     * @return the character at the specified position or DONE if the specified position is equal to getEndIndex()

     */

    public char setIndex(int position);

    /**

     * Returns the start index of the text.

     * @return the index at which the text begins.

     */

    public int getBeginIndex();

    /**

     * Returns the end index of the text.  This index is the index of the first

     * character following the end of the text.

     * @return the index after the last character in the text

     */

    public int getEndIndex();

    /**

     * Returns the current index.

     * @return the current index.

     */

    public int getIndex();

    /**

     * Create a copy of this iterator

     * @return A copy of this

     */

    public Object clone();

}