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 java.* package in JRE 1.8.0_191 rt.jar. Java source codes are also provided.

⏎ java/net/SocketOption.java

/*
 * Copyright (c) 2007, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package java.net;

/**
 * A socket option associated with a socket.
 *
 * <p> In the {@link java.nio.channels channels} package, the {@link
 * java.nio.channels.NetworkChannel} interface defines the {@link
 * java.nio.channels.NetworkChannel#setOption(SocketOption,Object) setOption}
 * and {@link java.nio.channels.NetworkChannel#getOption(SocketOption) getOption}
 * methods to set and query the channel's socket options.
 *
 * @param   <T>     The type of the socket option value.
 *
 * @since 1.7
 *
 * @see StandardSocketOptions
 */

public interface SocketOption<T> {

    /**
     * Returns the name of the socket option.
     *
     * @return the name of the socket option
     */
    String name();

    /**
     * Returns the type of the socket option value.
     *
     * @return the type of the socket option value
     */
    Class<T> type();
}

⏎ java/net/SocketOption.java

Or download all of them as a single archive file:

File name: jre-rt-java-1.8.0_191-src.zip
File size: 6664831 bytes
Release date: 2018-10-28
Download 

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