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/WindowsCheckBoxMenuItemUI.java

/*
 * Copyright (c) 1997, 2006, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
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 *
 *
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 *
 */

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

import java.awt.*;
import javax.swing.*;
import javax.swing.plaf.*;
import javax.swing.plaf.basic.*;

import com.sun.java.swing.plaf.windows.TMSchema.Part;
import com.sun.java.swing.plaf.windows.TMSchema.State;


/**
 * Windows check box menu item.
 * <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.
 */
public class WindowsCheckBoxMenuItemUI extends BasicCheckBoxMenuItemUI {

    final WindowsMenuItemUIAccessor accessor =
        new WindowsMenuItemUIAccessor() {

            public JMenuItem getMenuItem() {
                return menuItem;
            }

            public State getState(JMenuItem menuItem) {
                return WindowsMenuItemUI.getState(this, menuItem);
            }

            public Part getPart(JMenuItem menuItem) {
                return WindowsMenuItemUI.getPart(this, menuItem);
            }
    };
    public static ComponentUI createUI(JComponent b) {
        return new WindowsCheckBoxMenuItemUI();
    }

    @Override
    protected  void paintBackground(Graphics g, JMenuItem menuItem,
            Color bgColor) {
        if (WindowsMenuItemUI.isVistaPainting()) {
            WindowsMenuItemUI.paintBackground(accessor, g, menuItem, bgColor);
            return;
        }
        super.paintBackground(g, menuItem, bgColor);
    }
    /**
     * Method which renders the text of the current menu item.
     * <p>
     * @param g Graphics context
     * @param menuItem Current menu item to render
     * @param textRect Bounding rectangle to render the text.
     * @param text String to render
     * @since 1.4
     */
    protected void paintText(Graphics g, JMenuItem menuItem,
                             Rectangle textRect, String text) {
        if (WindowsMenuItemUI.isVistaPainting()) {
            WindowsMenuItemUI.paintText(accessor, g, menuItem,
                                        textRect, text);
            return;
        }
        ButtonModel model = menuItem.getModel();
        Color oldColor = g.getColor();

        if(model.isEnabled() && model.isArmed()) {
            g.setColor(selectionForeground); // Uses protected field.
        }

        WindowsGraphicsUtils.paintText(g, menuItem, textRect, text, 0);

        g.setColor(oldColor);
    }
}

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