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

⏎ java/beans/Customizer.java

/*
 * Copyright (c) 1996, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package java.beans;

/**
 * A customizer class provides a complete custom GUI for customizing
 * a target Java Bean.
 * <P>
 * Each customizer should inherit from the java.awt.Component class so
 * it can be instantiated inside an AWT dialog or panel.
 * <P>
 * Each customizer should have a null constructor.
 */

public interface Customizer {

    /**
     * Set the object to be customized.  This method should be called only
     * once, before the Customizer has been added to any parent AWT container.
     * @param bean  The object to be customized.
     */
    void setObject(Object bean);

    /**
     * Register a listener for the PropertyChange event.  The customizer
     * should fire a PropertyChange event whenever it changes the target
     * bean in a way that might require the displayed properties to be
     * refreshed.
     *
     * @param listener  An object to be invoked when a PropertyChange
     *          event is fired.
     */
     void addPropertyChangeListener(PropertyChangeListener listener);

    /**
     * Remove a listener for the PropertyChange event.
     *
     * @param listener  The PropertyChange listener to be removed.
     */
    void removePropertyChangeListener(PropertyChangeListener listener);

}

⏎ java/beans/Customizer.java

Or download all of them as a single archive file:

File name: jre-rt-java-1.8.0_191-src.zip
File size: 6664831 bytes
Release date: 2018-10-28
Download 

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

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