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

⏎ javax/swing/border/MatteBorder.java

/*
 * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */
package javax.swing.border;

import java.awt.Graphics;
import java.awt.Insets;
import java.awt.Component;
import java.awt.Color;

import javax.swing.Icon;

/**
 * A class which provides a matte-like border of either a solid color
 * or a tiled icon.
 * <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.  As of 1.4, support for long term storage
 * of all JavaBeans&trade;
 * has been added to the <code>java.beans</code> package.
 * Please see {@link java.beans.XMLEncoder}.
 *
 * @author Amy Fowler
 */
@SuppressWarnings("serial")
public class MatteBorder extends EmptyBorder
{
    protected Color color;
    protected Icon tileIcon;

    /**
     * Creates a matte border with the specified insets and color.
     * @param top the top inset of the border
     * @param left the left inset of the border
     * @param bottom the bottom inset of the border
     * @param right the right inset of the border
     * @param matteColor the color rendered for the border
     */
    public MatteBorder(int top, int left, int bottom, int right, Color matteColor)   {
        super(top, left, bottom, right);
        this.color = matteColor;
    }

    /**
     * Creates a matte border with the specified insets and color.
     * @param borderInsets the insets of the border
     * @param matteColor the color rendered for the border
     * @since 1.3
     */
    public MatteBorder(Insets borderInsets, Color matteColor)   {
        super(borderInsets);
        this.color = matteColor;
    }

    /**
     * Creates a matte border with the specified insets and tile icon.
     * @param top the top inset of the border
     * @param left the left inset of the border
     * @param bottom the bottom inset of the border
     * @param right the right inset of the border
     * @param tileIcon the icon to be used for tiling the border
     */
    public MatteBorder(int top, int left, int bottom, int right, Icon tileIcon)   {
        super(top, left, bottom, right);
        this.tileIcon = tileIcon;
    }

    /**
     * Creates a matte border with the specified insets and tile icon.
     * @param borderInsets the insets of the border
     * @param tileIcon the icon to be used for tiling the border
     * @since 1.3
     */
    public MatteBorder(Insets borderInsets, Icon tileIcon)   {
        super(borderInsets);
        this.tileIcon = tileIcon;
    }

    /**
     * Creates a matte border with the specified tile icon.  The
     * insets will be calculated dynamically based on the size of
     * the tile icon, where the top and bottom will be equal to the
     * tile icon's height, and the left and right will be equal to
     * the tile icon's width.
     * @param tileIcon the icon to be used for tiling the border
     */
    public MatteBorder(Icon tileIcon)   {
        this(-1,-1,-1,-1, tileIcon);
    }

    /**
     * Paints the matte border.
     */
    public void paintBorder(Component c, Graphics g, int x, int y, int width, int height) {
        Insets insets = getBorderInsets(c);
        Color oldColor = g.getColor();
        g.translate(x, y);

        // If the tileIcon failed loading, paint as gray.
        if (tileIcon != null) {
            color = (tileIcon.getIconWidth() == -1) ? Color.gray : null;
        }

        if (color != null) {
            g.setColor(color);
            g.fillRect(0, 0, width - insets.right, insets.top);
            g.fillRect(0, insets.top, insets.left, height - insets.top);
            g.fillRect(insets.left, height - insets.bottom, width - insets.left, insets.bottom);
            g.fillRect(width - insets.right, 0, insets.right, height - insets.bottom);

        } else if (tileIcon != null) {
            int tileW = tileIcon.getIconWidth();
            int tileH = tileIcon.getIconHeight();
            paintEdge(c, g, 0, 0, width - insets.right, insets.top, tileW, tileH);
            paintEdge(c, g, 0, insets.top, insets.left, height - insets.top, tileW, tileH);
            paintEdge(c, g, insets.left, height - insets.bottom, width - insets.left, insets.bottom, tileW, tileH);
            paintEdge(c, g, width - insets.right, 0, insets.right, height - insets.bottom, tileW, tileH);
        }
        g.translate(-x, -y);
        g.setColor(oldColor);

    }

    private void paintEdge(Component c, Graphics g, int x, int y, int width, int height, int tileW, int tileH) {
        g = g.create(x, y, width, height);
        int sY = -(y % tileH);
        for (x = -(x % tileW); x < width; x += tileW) {
            for (y = sY; y < height; y += tileH) {
                this.tileIcon.paintIcon(c, g, x, y);
            }
        }
        g.dispose();
    }

    /**
     * Reinitialize the insets parameter with this Border's current Insets.
     * @param c the component for which this border insets value applies
     * @param insets the object to be reinitialized
     * @since 1.3
     */
    public Insets getBorderInsets(Component c, Insets insets) {
        return computeInsets(insets);
    }

    /**
     * Returns the insets of the border.
     * @since 1.3
     */
    public Insets getBorderInsets() {
        return computeInsets(new Insets(0,0,0,0));
    }

    /* should be protected once api changes area allowed */
    private Insets computeInsets(Insets insets) {
        if (tileIcon != null && top == -1 && bottom == -1 &&
            left == -1 && right == -1) {
            int w = tileIcon.getIconWidth();
            int h = tileIcon.getIconHeight();
            insets.top = h;
            insets.right = w;
            insets.bottom = h;
            insets.left = w;
        } else {
            insets.left = left;
            insets.top = top;
            insets.right = right;
            insets.bottom = bottom;
        }
        return insets;
    }

    /**
     * Returns the color used for tiling the border or null
     * if a tile icon is being used.
     * @since 1.3
     */
    public Color getMatteColor() {
        return color;
    }

   /**
     * Returns the icon used for tiling the border or null
     * if a solid color is being used.
     * @since 1.3
     */
    public Icon getTileIcon() {
        return tileIcon;
    }

    /**
     * Returns whether or not the border is opaque.
     */
    public boolean isBorderOpaque() {
        // If a tileIcon is set, then it may contain transparent bits
        return color != null;
    }

}

⏎ javax/swing/border/MatteBorder.java

Or download all of them as a single archive file:

File name: jre-rt-javax-1.8.0_191-src.zip
File size: 5381005 bytes
Release date: 2018-10-28
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