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/WindowsMenuItemUI.java

/*
 * Copyright (c) 1997, 2014, 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.*;
import javax.swing.plaf.*;
import javax.swing.plaf.basic.*;

import sun.swing.SwingUtilities2;

import com.sun.java.swing.plaf.windows.TMSchema.*;
import com.sun.java.swing.plaf.windows.XPStyle.*;

/**
 * Windows rendition of the component.
 * <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 Igor Kushnirskiy
 */

public class WindowsMenuItemUI extends BasicMenuItemUI {
    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 c) {
        return new WindowsMenuItemUI();
    }

    /**
     * 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
     */
    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() || (menuItem instanceof JMenu &&
             model.isSelected()))) {
            g.setColor(selectionForeground); // Uses protected field.
        }

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

        g.setColor(oldColor);
    }

    @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);
    }

    static void paintBackground(WindowsMenuItemUIAccessor menuItemUI,
            Graphics g, JMenuItem menuItem, Color bgColor) {
        XPStyle xp = XPStyle.getXP();
        assert isVistaPainting(xp);
        if (isVistaPainting(xp)) {
            int menuWidth = menuItem.getWidth();
            int menuHeight = menuItem.getHeight();
            if (menuItem.isOpaque()) {
                Color oldColor = g.getColor();
                g.setColor(menuItem.getBackground());
                g.fillRect(0,0, menuWidth, menuHeight);
                g.setColor(oldColor);
            }
            Part part = menuItemUI.getPart(menuItem);
            Skin skin = xp.getSkin(menuItem, part);
            skin.paintSkin(g, 0 , 0,
                menuWidth,
                menuHeight,
                menuItemUI.getState(menuItem));
        }
    }

    static void paintText(WindowsMenuItemUIAccessor menuItemUI, Graphics g,
                                JMenuItem menuItem, Rectangle textRect,
                                String text) {
        assert isVistaPainting();
        if (isVistaPainting()) {
            State state = menuItemUI.getState(menuItem);

            /* part of it copied from WindowsGraphicsUtils.java */
            FontMetrics fm = SwingUtilities2.getFontMetrics(menuItem, g);
            int mnemIndex = menuItem.getDisplayedMnemonicIndex();
            // W2K Feature: Check to see if the Underscore should be rendered.
            if (WindowsLookAndFeel.isMnemonicHidden() == true) {
                mnemIndex = -1;
            }
            WindowsGraphicsUtils.paintXPText(menuItem,
                menuItemUI.getPart(menuItem), state,
                g, textRect.x,
                textRect.y + fm.getAscent(),
                text, mnemIndex);
        }
    }

    static State getState(WindowsMenuItemUIAccessor menuItemUI, JMenuItem menuItem) {
        State state;
        ButtonModel model = menuItem.getModel();
        if (model.isArmed()) {
            state = (model.isEnabled()) ? State.HOT : State.DISABLEDHOT;
        } else {
            state = (model.isEnabled()) ? State.NORMAL : State.DISABLED;
        }
        return state;
    }

    static Part getPart(WindowsMenuItemUIAccessor menuItemUI, JMenuItem menuItem) {
        return Part.MP_POPUPITEM;
    }

    /*
     * TODO idk can we use XPStyle.isVista?
     * is it possible that in some theme some Vista parts are not defined while
     * others are?
     */
    static boolean isVistaPainting(final XPStyle xp) {
        return xp != null && xp.isSkinDefined(null, Part.MP_POPUPITEM);
    }

    static boolean isVistaPainting() {
        return isVistaPainting(XPStyle.getXP());
    }
}

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