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/nio/ByteOrder.java

/*
 * Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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package java.nio;


/**
 * A typesafe enumeration for byte orders.
 *
 * @author Mark Reinhold
 * @author JSR-51 Expert Group
 * @since 1.4
 */

public final class ByteOrder {

    private String name;

    private ByteOrder(String name) {
        this.name = name;
    }

    /**
     * Constant denoting big-endian byte order.  In this order, the bytes of a
     * multibyte value are ordered from most significant to least significant.
     */
    public static final ByteOrder BIG_ENDIAN
        = new ByteOrder("BIG_ENDIAN");

    /**
     * Constant denoting little-endian byte order.  In this order, the bytes of
     * a multibyte value are ordered from least significant to most
     * significant.
     */
    public static final ByteOrder LITTLE_ENDIAN
        = new ByteOrder("LITTLE_ENDIAN");

    /**
     * Retrieves the native byte order of the underlying platform.
     *
     * <p> This method is defined so that performance-sensitive Java code can
     * allocate direct buffers with the same byte order as the hardware.
     * Native code libraries are often more efficient when such buffers are
     * used.  </p>
     *
     * @return  The native byte order of the hardware upon which this Java
     *          virtual machine is running
     */
    public static ByteOrder nativeOrder() {
        return Bits.byteOrder();
    }

    /**
     * Constructs a string describing this object.
     *
     * <p> This method returns the string <tt>"BIG_ENDIAN"</tt> for {@link
     * #BIG_ENDIAN} and <tt>"LITTLE_ENDIAN"</tt> for {@link #LITTLE_ENDIAN}.
     * </p>
     *
     * @return  The specified string
     */
    public String toString() {
        return name;
    }

}

⏎ java/nio/ByteOrder.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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