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

⏎ javax/accessibility/AccessibleAttributeSequence.java

/*
 * Copyright (c) 2003, 2005, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */
package javax.accessibility;

import javax.swing.text.AttributeSet;


/**
 * <P>The AccessibleAttributeSequence provides information about
 * a contiguous sequence of text attributes
 *
 * @see Accessible
 * @see Accessible#getAccessibleContext
 * @see AccessibleContext
 * @see AccessibleContext#getAccessibleText
 * @see AccessibleTextSequence
 *
 * @author       Lynn Monsanto
 */

/**
 * This class collects together the span of text that share the same
 * contiguous set of attributes, along with that set of attributes.  It
 * is used by implementors of the class <code>AccessibleContext</code> in
 * order to generate <code>ACCESSIBLE_TEXT_ATTRIBUTES_CHANGED</code> events.
 *
 * @see javax.accessibility.AccessibleContext
 * @see javax.accessibility.AccessibleContext#ACCESSIBLE_TEXT_ATTRIBUTES_CHANGED
 */
public class AccessibleAttributeSequence {
    /** The start index of the text sequence */
    public int startIndex;

    /** The end index of the text sequence */
    public int endIndex;

    /** The text attributes */
    public AttributeSet attributes;

    /**
     * Constructs an <code>AccessibleAttributeSequence</code> with the given
     * parameters.
     *
     * @param start the beginning index of the span of text
     * @param end the ending index of the span of text
     * @param attr the <code>AttributeSet</code> shared by this text span
     *
     * @since 1.6
     */
    public AccessibleAttributeSequence(int start, int end, AttributeSet attr) {
        startIndex = start;
        endIndex = end;
        attributes = attr;
    }

};

⏎ javax/accessibility/AccessibleAttributeSequence.java

Or download all of them as a single archive file:

File name: jre-rt-javax-1.8.0_191-src.zip
File size: 5381005 bytes
Release date: 2018-10-28
Download 

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

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

⇑ Download and Use JDK 8

⇑⇑ FAQ for JDK (Java Development Kit)