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

⏎ org/omg/CORBA/portable/CustomValue.java

/*
 * Copyright (c) 1999, 2000, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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/**
 * Defines the base interface for all custom value types
 * generated from IDL.
 *
 * All value types implement ValueBase either directly
 * or indirectly by implementing either the StreamableValue
 * or CustomValue interface.
 * @author OMG
 */

package org.omg.CORBA.portable;

import org.omg.CORBA.CustomMarshal;
/**
 * An extension of <code>ValueBase</code> that is implemented by custom value
 * types.
 */
public interface CustomValue extends ValueBase, CustomMarshal {

}

⏎ org/omg/CORBA/portable/CustomValue.java

Or download all of them as a single archive file:

File name: jre-rt-org-1.8.0_191-src.zip
File size: 951125 bytes
Release date: 2018-10-28
Download 

⇒ JRE 8 rt.jar - com.* Package Source Code

⇐ JRE 8 rt.jar - javax.* Package Source Code

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