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/Locator.java

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


/**
* com/sun/corba/se/spi/activation/Locator.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 interface Locator extends LocatorOperations, org.omg.CORBA.Object, org.omg.CORBA.portable.IDLEntity 
{
} // interface Locator

⏎ com/sun/corba/se/spi/activation/Locator.java

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