java/text/CollationElementIterator.java

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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;

/**
 * The <code>CollationElementIterator</code> class is used as an iterator
 * to walk through each character of an international string. Use the iterator
 * to return the ordering priority of the positioned character. The ordering
 * priority of a character, which we refer to as a key, defines how a character
 * is collated in the given collation object.
 *
 * <p>
 * For example, consider the following in Spanish:
 * <blockquote>
 * <pre>
 * "ca" &rarr; the first key is key('c') and second key is key('a').
 * "cha" &rarr; the first key is key('ch') and second key is key('a').
 * </pre>
 * </blockquote>
 * And in German,
 * <blockquote>
 * <pre>
 * "\u00e4b" &rarr; the first key is key('a'), the second key is key('e'), and
 * the third key is key('b').
 * </pre>
 * </blockquote>
 * The key of a character is an integer composed of primary order(short),
 * secondary order(byte), and tertiary order(byte). Java strictly defines
 * the size and signedness of its primitive data types. Therefore, the static
 * functions <code>primaryOrder</code>, <code>secondaryOrder</code>, and
 * <code>tertiaryOrder</code> return <code>int</code>, <code>short</code>,
 * and <code>short</code> respectively to ensure the correctness of the key
 * value.
 *
 * <p>
 * Example of the iterator usage,
 * <blockquote>
 * <pre>
 *
 *  String testString = "This is a test";
 *  Collator col = Collator.getInstance();
 *  if (col instanceof RuleBasedCollator) {
 *      RuleBasedCollator ruleBasedCollator = (RuleBasedCollator)col;
 *      CollationElementIterator collationElementIterator = ruleBasedCollator.getCollationElementIterator(testString);
 *      int primaryOrder = CollationElementIterator.primaryOrder(collationElementIterator.next());
 *          :
 *  }
 * </pre>
 * </blockquote>
 *
 * <p>
 * <code>CollationElementIterator.next</code> returns the collation order
 * of the next character. A collation order consists of primary order,
 * secondary order and tertiary order. The data type of the collation
 * order is <strong>int</strong>. The first 16 bits of a collation order
 * is its primary order; the next 8 bits is the secondary order and the
 * last 8 bits is the tertiary order.
 *
 * <p><b>Note:</b> <code>CollationElementIterator</code> is a part of
 * <code>RuleBasedCollator</code> implementation. It is only usable
 * with <code>RuleBasedCollator</code> instances.
 *
 * @see                Collator
 * @see                RuleBasedCollator
 * @author             Helena Shih, Laura Werner, Richard Gillam
 */
public final class CollationElementIterator
{
    /**
     * Null order which indicates the end of string is reached by the
     * cursor.
     */
    // Android-changed: use ICU CollationElementIterator constant.
    public final static int NULLORDER = android.icu.text.CollationElementIterator.NULLORDER;

    // Android-removed: internal constructors.

    // Android-added: ICU iterator to delegate to.
    private android.icu.text.CollationElementIterator icuIterator;

   // Android-added: internal constructor taking an ICU CollationElementIterator.
    CollationElementIterator(android.icu.text.CollationElementIterator iterator) {
        icuIterator = iterator;
    }

    /**
     * Resets the cursor to the beginning of the string.  The next call
     * to next() will return the first collation element in the string.
     */
    public void reset()
    {
        // Android-changed: delegate to ICU CollationElementIterator.
        icuIterator.reset();
    }

    /**
     * Get the next collation element in the string.  <p>This iterator iterates
     * over a sequence of collation elements that were built from the string.
     * Because there isn't necessarily a one-to-one mapping from characters to
     * collation elements, this doesn't mean the same thing as "return the
     * collation element [or ordering priority] of the next character in the
     * string".</p>
     * <p>This function returns the collation element that the iterator is currently
     * pointing to and then updates the internal pointer to point to the next element.
     * previous() updates the pointer first and then returns the element.  This
     * means that when you change direction while iterating (i.e., call next() and
     * then call previous(), or call previous() and then call next()), you'll get
     * back the same element twice.</p>
     *
     * @return the next collation element
     */
    public int next()
    {
        // Android-changed: delegate to ICU CollationElementIterator.
        return icuIterator.next();
    }

    /**
     * Get the previous collation element in the string.  <p>This iterator iterates
     * over a sequence of collation elements that were built from the string.
     * Because there isn't necessarily a one-to-one mapping from characters to
     * collation elements, this doesn't mean the same thing as "return the
     * collation element [or ordering priority] of the previous character in the
     * string".</p>
     * <p>This function updates the iterator's internal pointer to point to the
     * collation element preceding the one it's currently pointing to and then
     * returns that element, while next() returns the current element and then
     * updates the pointer.  This means that when you change direction while
     * iterating (i.e., call next() and then call previous(), or call previous()
     * and then call next()), you'll get back the same element twice.</p>
     *
     * @return the previous collation element
     * @since 1.2
     */
    public int previous()
    {
        // Android-changed: delegate to ICU CollationElementIterator.
        return icuIterator.previous();
    }

    /**
     * Return the primary component of a collation element.
     * @param order the collation element
     * @return the element's primary component
     */
    public final static int primaryOrder(int order)
    {
        // Android-changed: delegate to ICU CollationElementIterator.
        return android.icu.text.CollationElementIterator.primaryOrder(order);
    }
    /**
     * Return the secondary component of a collation element.
     * @param order the collation element
     * @return the element's secondary component
     */
    public final static short secondaryOrder(int order)
    {
        // Android-changed: delegate to ICU CollationElementIterator.
       return (short) android.icu.text.CollationElementIterator.secondaryOrder(order);
    }
    /**
     * Return the tertiary component of a collation element.
     * @param order the collation element
     * @return the element's tertiary component
     */
    public final static short tertiaryOrder(int order)
    {
        // Android-changed: delegate to ICU CollationElementIterator.
        return (short) android.icu.text.CollationElementIterator.tertiaryOrder(order);
    }

    /**
     * Sets the iterator to point to the collation element corresponding to
     * the specified character (the parameter is a CHARACTER offset in the
     * original string, not an offset into its corresponding sequence of
     * collation elements).  The value returned by the next call to next()
     * will be the collation element corresponding to the specified position
     * in the text.  If that position is in the middle of a contracting
     * character sequence, the result of the next call to next() is the
     * collation element for that sequence.  This means that getOffset()
     * is not guaranteed to return the same value as was passed to a preceding
     * call to setOffset().
     *
     * @param newOffset The new character offset into the original text.
     * @since 1.2
     */
    @SuppressWarnings("deprecation") // getBeginIndex, getEndIndex and setIndex are deprecated
    public void setOffset(int newOffset)
    {
        // Android-changed: delegate to ICU CollationElementIterator.
        icuIterator.setOffset(newOffset);
    }

    /**
     * Returns the character offset in the original text corresponding to the next
     * collation element.  (That is, getOffset() returns the position in the text
     * corresponding to the collation element that will be returned by the next
     * call to next().)  This value will always be the index of the FIRST character
     * corresponding to the collation element (a contracting character sequence is
     * when two or more characters all correspond to the same collation element).
     * This means if you do setOffset(x) followed immediately by getOffset(), getOffset()
     * won't necessarily return x.
     *
     * @return The character offset in the original text corresponding to the collation
     * element that will be returned by the next call to next().
     * @since 1.2
     */
    public int getOffset()
    {
        // Android-changed: delegate to ICU CollationElementIterator.
        return icuIterator.getOffset();
    }


    /**
     * Return the maximum length of any expansion sequences that end
     * with the specified comparison order.
     * @param order a collation order returned by previous or next.
     * @return the maximum length of any expansion sequences ending
     *         with the specified order.
     * @since 1.2
     */
    public int getMaxExpansion(int order)
    {
        // Android-changed: delegate to ICU CollationElementIterator.
        return icuIterator.getMaxExpansion(order);
    }

    /**
     * Set a new string over which to iterate.
     *
     * @param source  the new source text
     * @since 1.2
     */
    public void setText(String source)
    {
        // Android-changed: delegate to ICU CollationElementIterator.
        icuIterator.setText(source);
    }

    /**
     * Set a new string over which to iterate.
     *
     * @param source  the new source text.
     * @since 1.2
     */
    public void setText(CharacterIterator source)
    {
        // Android-changed: delegate to ICU CollationElementIterator.
        icuIterator.setText(source);
    }

    // Android-removed: private helper methods and fields.
}