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

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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

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package java.util.regex;

/**

 * The result of a match operation.

 *

 * <p>This interface contains query methods used to determine the

 * results of a match against a regular expression. The match boundaries,

 * groups and group boundaries can be seen but not modified through

 * a {@code MatchResult}.

 *

 * @author  Michael McCloskey

 * @see Matcher

 * @since 1.5

 */

public interface MatchResult {

    /**

     * Returns the start index of the match.

     *

     * @return  The index of the first character matched

     *

     * @throws  IllegalStateException

     *          If no match has yet been attempted,

     *          or if the previous match operation failed

     */

    public int start();

    /**

     * Returns the start index of the subsequence captured by the given group

     * during this match.

     *

     * <p> <a href="Pattern.html#cg">Capturing groups</a> are indexed from left

     * to right, starting at one.  Group zero denotes the entire pattern, so

     * the expression <i>m.</i>{@code start(0)} is equivalent to

     * <i>m.</i>{@code start()}.  </p>

     *

     * @param  group

     *         The index of a capturing group in this matcher's pattern

     *

     * @return  The index of the first character captured by the group,

     *          or {@code -1} if the match was successful but the group

     *          itself did not match anything

     *

     * @throws  IllegalStateException

     *          If no match has yet been attempted,

     *          or if the previous match operation failed

     *

     * @throws  IndexOutOfBoundsException

     *          If there is no capturing group in the pattern

     *          with the given index

     */

    public int start(int group);

    /**

     * Returns the offset after the last character matched.

     *

     * @return  The offset after the last character matched

     *

     * @throws  IllegalStateException

     *          If no match has yet been attempted,

     *          or if the previous match operation failed

     */

    public int end();

    /**

     * Returns the offset after the last character of the subsequence

     * captured by the given group during this match.

     *

     * <p> <a href="Pattern.html#cg">Capturing groups</a> are indexed from left

     * to right, starting at one.  Group zero denotes the entire pattern, so

     * the expression <i>m.</i>{@code end(0)} is equivalent to

     * <i>m.</i>{@code end()}.  </p>

     *

     * @param  group

     *         The index of a capturing group in this matcher's pattern

     *

     * @return  The offset after the last character captured by the group,

     *          or {@code -1} if the match was successful

     *          but the group itself did not match anything

     *

     * @throws  IllegalStateException

     *          If no match has yet been attempted,

     *          or if the previous match operation failed

     *

     * @throws  IndexOutOfBoundsException

     *          If there is no capturing group in the pattern

     *          with the given index

     */

    public int end(int group);

    /**

     * Returns the input subsequence matched by the previous match.

     *

     * <p> For a matcher <i>m</i> with input sequence <i>s</i>,

     * the expressions <i>m.</i>{@code group()} and

     * <i>s.</i>{@code substring(}<i>m.</i>{@code start(),}&nbsp;<i>m.</i>{@code end())}

     * are equivalent.  </p>

     *

     * <p> Note that some patterns, for example {@code a*}, match the empty

     * string.  This method will return the empty string when the pattern

     * successfully matches the empty string in the input.  </p>

     *

     * @return The (possibly empty) subsequence matched by the previous match,

     *         in string form

     *

     * @throws  IllegalStateException

     *          If no match has yet been attempted,

     *          or if the previous match operation failed

     */

    public String group();

    /**

     * Returns the input subsequence captured by the given group during the

     * previous match operation.

     *

     * <p> For a matcher <i>m</i>, input sequence <i>s</i>, and group index

     * <i>g</i>, the expressions <i>m.</i>{@code group(}<i>g</i>{@code )} and

     * <i>s.</i>{@code substring(}<i>m.</i>{@code start(}<i>g</i>{@code

     * ),}&nbsp;<i>m.</i>{@code end(}<i>g</i>{@code ))}

     * are equivalent.  </p>

     *

     * <p> <a href="Pattern.html#cg">Capturing groups</a> are indexed from left

     * to right, starting at one.  Group zero denotes the entire pattern, so

     * the expression {@code m.group(0)} is equivalent to {@code m.group()}.

     * </p>

     *

     * <p> If the match was successful but the group specified failed to match

     * any part of the input sequence, then {@code null} is returned. Note

     * that some groups, for example {@code (a*)}, match the empty string.

     * This method will return the empty string when such a group successfully

     * matches the empty string in the input.  </p>

     *

     * @param  group

     *         The index of a capturing group in this matcher's pattern

     *

     * @return  The (possibly empty) subsequence captured by the group

     *          during the previous match, or {@code null} if the group

     *          failed to match part of the input

     *

     * @throws  IllegalStateException

     *          If no match has yet been attempted,

     *          or if the previous match operation failed

     *

     * @throws  IndexOutOfBoundsException

     *          If there is no capturing group in the pattern

     *          with the given index

     */

    public String group(int group);

    /**

     * Returns the number of capturing groups in this match result's pattern.

     *

     * <p> Group zero denotes the entire pattern by convention. It is not

     * included in this count.

     *

     * <p> Any non-negative integer smaller than or equal to the value

     * returned by this method is guaranteed to be a valid group index for

     * this matcher.  </p>

     *

     * @return The number of capturing groups in this matcher's pattern

     */

    public int groupCount();

}