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/javadoc/package-info.java

/*
 * Copyright (c) 1998, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

/**
The Doclet API (also called the Javadoc API) provides a mechanism
for clients to inspect the source-level structure of programs and
libraries, including javadoc comments embedded in the source.
This is useful for documentation, program checking, automatic
code generation and many other tools.
<p>

Doclets are invoked by javadoc and use this API to write out
program information to files.  For example, the standard doclet is called
by default and writes out documentation to HTML files.
<p>

The invocation is defined by the abstract {@link com.sun.javadoc.Doclet} class
-- the entry point is the {@link com.sun.javadoc.Doclet#start(RootDoc) start} method:
<pre>
    public static boolean <b>start</b>(RootDoc root)
</pre>
The {@link com.sun.javadoc.RootDoc} instance holds the root of the program structure
information. From this root all other program structure
information can be extracted.
<p>

<a name="terminology"></a>
<h3>Terminology</h3>

<a name="included"></a>
When calling javadoc, you pass in package names and source file names --
these are called the <em>specified</em> packages and classes.
You also pass in Javadoc options; the <em>access control</em> Javadoc options
(<code>-public</code>, <code>-protected</code>, <code>-package</code>,
and <code>-private</code>) filter program elements, producing a
result set, called the <em>included</em> set, or "documented" set.
(The unfiltered set is also available through
{@link com.sun.javadoc.PackageDoc#allClasses(boolean) allClasses(false)}.)
<p>

<a name="class"></a>
Throughout this API, the term <em>class</em> is normally a
shorthand for "class or interface", as in: {@link com.sun.javadoc.ClassDoc},
{@link com.sun.javadoc.PackageDoc#allClasses() allClasses()}, and
{@link com.sun.javadoc.PackageDoc#findClass(String) findClass(String)}.
In only a couple of other places, it means "class, as opposed to interface",
as in:  {@link com.sun.javadoc.Doc#isClass()}.
In the second sense, this API calls out four kinds of classes:
{@linkplain com.sun.javadoc.Doc#isOrdinaryClass() ordinary classes},
{@linkplain com.sun.javadoc.Doc#isEnum() enums},
{@linkplain com.sun.javadoc.Doc#isError() errors} and
{@linkplain com.sun.javadoc.Doc#isException() exceptions}.
Throughout the API, the detailed description of each program element
describes explicitly which meaning is being used.
<p>

<a name="qualified"></a>
A <em>qualified</em> class or interface name is one that has its package
name prepended to it, such as <code>java.lang.String</code>.  A non-qualified
name has no package name, such as <code>String</code>.
<p>

<a name="example"></a>
<h3>Example</h3>

The following is an example doclet that
displays information in the <code>@param</code> tags of the processed
classes:
<pre>
import com.sun.javadoc.*;

public class ListParams extends <font color=red title="Doclet API">Doclet</font> {

    public static boolean start(<font color=red title="Doclet API">RootDoc</font> root) {
        <font color=red title="Doclet API">ClassDoc</font>[] classes = root.<font color=red title="Doclet API">classes</font>();
        for (int i = 0; i < classes.length; ++i) {
            <font color=red title="Doclet API">ClassDoc</font> cd = classes[i];
            printMembers(cd.<font color=red title="Doclet API">constructors</font>());
            printMembers(cd.<font color=red title="Doclet API">methods</font>());
        }
        return true;
    }

    static void printMembers(<font color=red title="Doclet API">ExecutableMemberDoc</font>[] mems) {
        for (int i = 0; i < mems.length; ++i) {
            <font color=red title="Doclet API">ParamTag</font>[] params = mems[i].<font color=red title="Doclet API">paramTags</font>();
            System.out.println(mems[i].<font color=red title="Doclet API">qualifiedName</font>());
            for (int j = 0; j < params.length; ++j) {
                System.out.println("   " + params[j].<font color=red title="Doclet API">parameterName</font>()
                    + " - " + params[j].<font color=red title="Doclet API">parameterComment</font>());
            }
        }
    }
}
</pre>
Interfaces and methods from the Javadoc API are marked in
<font color=red title="Doclet API">red</font>.
{@link com.sun.javadoc.Doclet Doclet} is an abstract class that specifies
the invocation interface for doclets,
{@link com.sun.javadoc.Doclet Doclet} holds class or interface information,
{@link com.sun.javadoc.ExecutableMemberDoc} is a
superinterface of {@link com.sun.javadoc.MethodDoc} and
{@link com.sun.javadoc.ConstructorDoc},
and {@link com.sun.javadoc.ParamTag} holds information
from "<code>@param</code>" tags.
<p>
This doclet when invoked with a command line like:
<pre>
    javadoc -doclet ListParams -sourcepath &lt;source-location&gt; java.util
</pre>
producing output like:
<pre>
    ...
    java.util.ArrayList.add
       index - index at which the specified element is to be inserted.
       element - element to be inserted.
    java.util.ArrayList.remove
       index - the index of the element to removed.
    ...

</pre>
@see com.sun.javadoc.Doclet
@see com.sun.javadoc.RootDoc
*/
@jdk.Exported
package com.sun.javadoc;

⏎ com/sun/javadoc/package-info.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 

⇒ Backup JDK 8 Installation Directory

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

⇑ Download and Use JDK 8

⇑⇑ FAQ for JDK (Java Development Kit)