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/corba/se/spi/activation/ServerAlreadyInstalled.java

package com.sun.corba.se.spi.activation;


/**
* com/sun/corba/se/spi/activation/ServerAlreadyInstalled.java .
* Generated by the IDL-to-Java compiler (portable), version "3.2"
* from c:/re/workspace/8-2-build-windows-amd64-cygwin/jdk8u191/11896/corba/src/share/classes/com/sun/corba/se/spi/activation/activation.idl
* Saturday, October 6, 2018 9:30:40 AM PDT
*/

public final class ServerAlreadyInstalled extends org.omg.CORBA.UserException
{
  public int serverId = (int)0;

  public ServerAlreadyInstalled ()
  {
    super(ServerAlreadyInstalledHelper.id());
  } // ctor

  public ServerAlreadyInstalled (int _serverId)
  {
    super(ServerAlreadyInstalledHelper.id());
    serverId = _serverId;
  } // ctor


  public ServerAlreadyInstalled (String $reason, int _serverId)
  {
    super(ServerAlreadyInstalledHelper.id() + "  " + $reason);
    serverId = _serverId;
  } // ctor

} // class ServerAlreadyInstalled

⏎ com/sun/corba/se/spi/activation/ServerAlreadyInstalled.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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