JRE 8 rt.jar is the JAR file for JRE 8 RT (Runtime) libraries. JRE (Java Runtime) 8 is the runtime environment included in JDK 8. JRE 8 rt.jar libraries are divided into 6 packages:

com.* - Internal Oracle and Sun Microsystems libraries
java.* - Standard Java API libraries.
javax.* - Extended Java API libraries.
jdk.* -  JDK supporting libraries.
org.* - Third party libraries.
sun.* - Old libraries developed by Sun Microsystems.

JAR File Information:

Directory of C:\fyicenter\jdk-1.8.0_191\jre\lib
      63,596,151 rt.jar

Here is the list of Java classes of the com.* package in JRE 1.8.0_191 rt.jar. Java source codes are also provided.

⏎ com/sun/org/apache/regexp/internal/REUtil.java

/*
 * Copyright (c) 2007, 2018, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
/*
 * Copyright 1999-2004 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.sun.org.apache.regexp.internal;

/**
 * This is a class that contains utility helper methods for this package.
 *
 * @author <a href="mailto:jonl@muppetlabs.com">Jonathan Locke</a>
 */
public class REUtil
{
    /** complex: */
    private static final String complexPrefix = "complex:";

    /**
     * Creates a regular expression, permitting simple or complex syntax
     * @param expression The expression, beginning with a prefix if it's complex or
     * having no prefix if it's simple
     * @param matchFlags Matching style flags
     * @return The regular expression object
     * @exception RESyntaxException thrown in case of error
     */
    public static RE createRE(String expression, int matchFlags) throws RESyntaxException
    {
        if (expression.startsWith(complexPrefix))
        {
            return new RE(expression.substring(complexPrefix.length()), matchFlags);
        }
        return new RE(RE.simplePatternToFullRegularExpression(expression), matchFlags);
    }

    /**
     * Creates a regular expression, permitting simple or complex syntax
     * @param expression The expression, beginning with a prefix if it's complex or
     * having no prefix if it's simple
     * @return The regular expression object
     * @exception RESyntaxException thrown in case of error
     */
    public static RE createRE(String expression) throws RESyntaxException
    {
        return createRE(expression, RE.MATCH_NORMAL);
    }
}

⏎ com/sun/org/apache/regexp/internal/REUtil.java

Or download all of them as a single archive file:

File name: jre-rt-com-1.8.0_191-src.zip
File size: 8099783 bytes
Release date: 2018-10-28
Download 

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