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A maven release for nashorn. Changed nothing, just put it to maven.
There is a newer version: jdk8u265-b01-x3
/*
 * Copyright (c) 2010, 2019, 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
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package jdk.nashorn.internal.runtime.regexp;

import static java.util.regex.Pattern.CASE_INSENSITIVE;
import static java.util.regex.Pattern.MULTILINE;
import static java.util.regex.Pattern.UNICODE_CASE;

import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;
import jdk.nashorn.internal.runtime.ParserException;

/**
 * Default regular expression implementation based on java.util.regex package.
 *
 * Note that this class is not thread-safe as it stores the current match result
 * and the string being matched in instance fields.
 */
public class JdkRegExp extends RegExp {

    /** Java regexp pattern to use for match. We compile to one of these */
    private Pattern pattern;

    /**
     * Construct a Regular expression from the given {@code source} and {@code flags} strings.
     *
     * @param source RegExp source string
     * @param flags RegExp flag string
     * @throws ParserException if flags is invalid or source string has syntax error.
     */
    public JdkRegExp(final String source, final String flags) throws ParserException {
        super(source, flags);

        int intFlags = 0;

        if (isIgnoreCase()) {
            intFlags |= CASE_INSENSITIVE | UNICODE_CASE;
        }
        if (isMultiline()) {
            intFlags |= MULTILINE;
        }

        try {
            RegExpScanner parsed;

            try {
                parsed = RegExpScanner.scan(source);
            } catch (final PatternSyntaxException e) {
                // refine the exception with a better syntax error, if this
                // passes, just rethrow what we have
                Pattern.compile(source, intFlags);
                throw e;
            }

            if (parsed != null) {
                this.pattern = Pattern.compile(parsed.getJavaPattern(), intFlags);
                this.groupsInNegativeLookahead = parsed.getGroupsInNegativeLookahead();
            }
        } catch (final PatternSyntaxException e2) {
            throwParserException("syntax", e2.getMessage());
        } catch (StackOverflowError e3) {
            throw new RuntimeException(e3);
        }
    }

    @Override
    public RegExpMatcher match(final String str) {
        if (pattern == null) {
            return null; // never matches or similar, e.g. a[]
        }

        return new DefaultMatcher(str);
    }

    class DefaultMatcher implements RegExpMatcher {
        final String input;
        final Matcher defaultMatcher;

        DefaultMatcher(final String input) {
            this.input = input;
            this.defaultMatcher = pattern.matcher(input);
        }

        @Override
        public boolean search(final int start) {
            return defaultMatcher.find(start);
        }

        @Override
        public String getInput() {
            return input;
        }

        @Override
        public int start() {
            return defaultMatcher.start();
        }

        @Override
        public int start(final int group) {
            return defaultMatcher.start(group);
        }

        @Override
        public int end() {
            return defaultMatcher.end();
        }

        @Override
        public int end(final int group) {
            return defaultMatcher.end(group);
        }

        @Override
        public String group() {
            return defaultMatcher.group();
        }

        @Override
        public String group(final int group) {
            return defaultMatcher.group(group);
        }

        @Override
        public int groupCount() {
            return defaultMatcher.groupCount();
        }
    }

}