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/WindowsSpinnerUI.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 java.awt.event.*;

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

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


public class WindowsSpinnerUI extends BasicSpinnerUI {
    public static ComponentUI createUI(JComponent c) {
        return new WindowsSpinnerUI();
    }

    /**
     * {@inheritDoc}
     * @since 1.6
     */
    public void paint(Graphics g, JComponent c) {
        if (XPStyle.getXP() != null) {
            paintXPBackground(g, c);
        }
        super.paint(g,c);
    }

    private State getXPState(JComponent c) {
        State state = State.NORMAL;
        if (!c.isEnabled()) {
            state = State.DISABLED;
        }
        return state;
    }

    private void paintXPBackground(Graphics g, JComponent c) {
        XPStyle xp = XPStyle.getXP();
        if (xp == null) {
            return;
        }
        Skin skin = xp.getSkin(c, Part.EP_EDIT);
        State state = getXPState(c);
        skin.paintSkin(g, 0, 0, c.getWidth(), c.getHeight(), state);
    }

    protected Component createPreviousButton() {
        if (XPStyle.getXP() != null) {
            JButton xpButton = new XPStyle.GlyphButton(spinner, Part.SPNP_DOWN);
            Dimension size = UIManager.getDimension("Spinner.arrowButtonSize");
            xpButton.setPreferredSize(size);
            xpButton.setRequestFocusEnabled(false);
            installPreviousButtonListeners(xpButton);
            return xpButton;
        }
        return super.createPreviousButton();
    }

    protected Component createNextButton() {
        if (XPStyle.getXP() != null) {
            JButton xpButton = new XPStyle.GlyphButton(spinner, Part.SPNP_UP);
            Dimension size = UIManager.getDimension("Spinner.arrowButtonSize");
            xpButton.setPreferredSize(size);
            xpButton.setRequestFocusEnabled(false);
            installNextButtonListeners(xpButton);
            return xpButton;
        }
        return super.createNextButton();
    }

    private UIResource getUIResource(Object[] listeners) {
        for (int counter = 0; counter < listeners.length; counter++) {
            if (listeners[counter] instanceof UIResource) {
                return (UIResource)listeners[counter];
            }
        }
        return null;
    }
}

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