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/java/swing/plaf/windows/WindowsSplitPaneDivider.java

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

package com.sun.java.swing.plaf.windows;

import java.awt.*;
import javax.swing.JSplitPane;
import javax.swing.UIManager;
import javax.swing.plaf.basic.BasicSplitPaneUI;
import javax.swing.plaf.basic.BasicSplitPaneDivider;


/**
 * Divider used for Windows split pane.
 * <p>
 * <strong>Warning:</strong>
 * Serialized objects of this class will not be compatible with
 * future Swing releases.  The current serialization support is appropriate
 * for short term storage or RMI between applications running the same
 * version of Swing.  A future release of Swing will provide support for
 * long term persistence.
 *
 * @author Jeff Dinkins
 */
public class WindowsSplitPaneDivider extends BasicSplitPaneDivider
{

    /**
     * Creates a new Windows SplitPaneDivider
     */
    public WindowsSplitPaneDivider(BasicSplitPaneUI ui) {
        super(ui);
    }

    /**
      * Paints the divider.
      */
    public void paint(Graphics g) {
        Color bgColor = (splitPane.hasFocus()) ?
                            UIManager.getColor("SplitPane.shadow") :
                            getBackground();
        Dimension size = getSize();

        if(bgColor != null) {
            g.setColor(bgColor);
            g.fillRect(0, 0, size.width, size.height);
        }
        super.paint(g);
    }
}

⏎ com/sun/java/swing/plaf/windows/WindowsSplitPaneDivider.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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