Thread: JButton...

i cant make the button appear on my panel...
why?

package xTestx;
 
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JSlider;
import javax.swing.JButton;
import javax.swing.SwingConstants;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
 
import java.awt.Color;
import java.awt.Label;
import java.awt.Point;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.HeadlessException;
 
/**
 * Simple JSlider.
 *
 * @author  
 */
 
public class PropertiesWindow implements ChangeListener {
 
    JFrame propertiesWindow;
 
    JPanel windowPanel;
 
    JButton button;
 
    JSlider widthSlider;
    JSlider heightSlider;
    JSlider pointXSlider;
    JSlider pointYSlider;
 
    JSlider redSchemeSlider;
    JSlider blueSchemeSlider;
    JSlider greenSchemeSlider;
 
    JLabel widthLabel;
    JLabel heightLabel;
    JLabel pointYLabel;
    JLabel pointXLabel;
 
    JLabel redSchemeLabel;
    JLabel blueSchemeLabel;
    JLabel greenSchemeLabel;
 
    // the spot where the sliders color combination will be displayed
    Label colorSpot;
 
    // the color spot label name
    Label spotLabel;
 
    // center point for the shape
    Point centerPoint;
 
    // dimension of the shape
    Dimension shapeDimension;
 
    // minimum value for the width of the shape
    private static final int WIDTH_MIN_VALUE = 100;
 
    // maximum value for width of the shape
    private static final int WIDTH_MAX_VALUE = 500;
 
    // minimum value for the height of the shape
    private static final int HEIGHT_MIN_VALUE = 100;
 
    // maximum value for the height of the shape
    private static final int HEIGHT_MAX_VALUE = 500;
 
    // minimum value for the center point (point x) of the shape
    private static final int MIN_POINT_X = 200;
 
    // maximum value for the center point (point x) of the shape
    private static final int MAX_POINT_X = 800;
 
    // minimum value for the center point (point y) of the shape
    private static final int MIN_POINT_Y = 100;
 
    // maximum value for the center point (point  y) of the shape
    private static final int MAX_POINT_Y = 500;
 
    // constant value for color scheme slider's minor tick
    private static final int COLOR_SLIDER_MINOR_TICK = 5;
 
    // constant value for color scheme slider's major tick
    private static final int COLOR_SLIDER_MAJOR_TICK = 10;
 
    // constant value of minor tick for the geometric pattern sliders
    private static final int MINOR_TICK = 10;
 
    // constant value of major tick for the geometric pattern sliders
    private static final int MAJOR_TICK = 100;
 
    public void showPropertyWindow() throws HeadlessException {
 
        propertiesWindow = new JFrame("Properties Window");
 
        windowPanel = new JPanel();
 
        button = new JButton("My Button");
 
        widthSlider = new JSlider(WIDTH_MIN_VALUE, WIDTH_MAX_VALUE);
        heightSlider = new JSlider(HEIGHT_MIN_VALUE, HEIGHT_MAX_VALUE);
        pointXSlider = new JSlider(MIN_POINT_X, MAX_POINT_X);
        pointYSlider = new JSlider(MIN_POINT_Y, MAX_POINT_Y);
 
        // sliders for the adjustment of the color
        redSchemeSlider = new JSlider(SwingConstants.VERTICAL, 0 , 255, 0);
        blueSchemeSlider = new JSlider(SwingConstants.VERTICAL, 0, 255, 0);
        greenSchemeSlider = new JSlider(SwingConstants.VERTICAL, 0 ,255, 0);
 
        widthLabel = new JLabel();
        heightLabel = new JLabel();
        pointXLabel = new JLabel();
        pointYLabel = new JLabel();
 
        // Label for each color
        redSchemeLabel = new JLabel();
        blueSchemeLabel = new JLabel();
        greenSchemeLabel = new JLabel();
 
        // spot where the color that will be generated by the color sliders is displayed
        colorSpot = new Label();
 
        // Label for the width value slider
        widthLabel.setText("Width  :  ");
        widthLabel.setBounds(20, 10, 50, 40);
 
        // set the slider properties for the width
        widthSlider.setBounds(20, 35, 250, 50);
        widthSlider.setMinorTickSpacing(MINOR_TICK);
        widthSlider.setMajorTickSpacing(MAJOR_TICK);
        widthSlider.setPaintTicks(true);
        widthSlider.setPaintLabels(true);
        widthSlider.setToolTipText("Width");
        widthSlider.setForeground(Color.GRAY);
        widthSlider.addChangeListener(this);
 
        // Label for the height value slider
        heightLabel.setText("Height  :  ");
        heightLabel.setBounds(20, 90, 60, 70);
 
        // set the slider properties for the height
        heightSlider.setBounds(20, 135, 250, 45);
        heightSlider.setMinorTickSpacing(MINOR_TICK);
        heightSlider.setMajorTickSpacing(MAJOR_TICK);
        heightSlider.setPaintTicks(true);
        heightSlider.setPaintLabels(true);
        heightSlider.setToolTipText("Height");
        heightSlider.setForeground(Color.GRAY);
 
        // Label for the point x (center point)
        pointXLabel.setText("Point x  :  ");
        pointXLabel.setBounds(20, 175, 70, 100);
 
        // set the properties of the point x(center point) slider
        pointXSlider.setBounds(20, 230, 250, 50);
        pointXSlider.setMinorTickSpacing(MINOR_TICK);
        pointXSlider.setMajorTickSpacing(MAJOR_TICK);
        pointXSlider.setPaintTicks(true);
        pointXSlider.setPaintLabels(true);
        pointXSlider.setToolTipText("Center Point (x)");
        pointXSlider.setForeground(Color.GRAY);
 
        // Label for the point y (center point)
        pointYLabel.setText("Point y  :  ");
        pointYLabel.setBounds(20, 240, 70, 155);
 
        // set the properties of the point y(center point) slider
        pointYSlider.setBounds(20, 330, 250, 45);
        pointYSlider.setMinorTickSpacing(MINOR_TICK);
        pointYSlider.setMajorTickSpacing(MAJOR_TICK);
        pointYSlider.setPaintTicks(true);
        pointYSlider.setPaintLabels(true);
        pointYSlider.setToolTipText("Center Point (y)");
        pointYSlider.setForeground(Color.GRAY);
 
        // Label for each of the color scheme slider
        redSchemeLabel.setText("Red  :  ");
        redSchemeLabel.setBounds(300, 5, 50 , 50);
        greenSchemeLabel.setText("Green  :  ");
        greenSchemeLabel.setBounds(530, 5, 50, 50);
        blueSchemeLabel.setText("Blue  :  ");
        blueSchemeLabel.setBounds(420, 5, 50, 50);
 
        // set the properties of the red color scheme slider
        redSchemeSlider.setBounds(310, 40, 50, 280);
        redSchemeSlider.setMinorTickSpacing(COLOR_SLIDER_MINOR_TICK);
        redSchemeSlider.setMajorTickSpacing(COLOR_SLIDER_MAJOR_TICK);
        redSchemeSlider.setPaintTicks(true);
        redSchemeSlider.setPaintLabels(false);
        redSchemeSlider.setToolTipText("Red");
        redSchemeSlider.setForeground(Color.RED);
        redSchemeSlider.addChangeListener(this);
 
        // set the properties of the green color scheme slider
        greenSchemeSlider.setBounds(550, 40, 50, 280);
        greenSchemeSlider.setMinorTickSpacing(COLOR_SLIDER_MINOR_TICK);
        greenSchemeSlider.setMajorTickSpacing(COLOR_SLIDER_MAJOR_TICK);
        greenSchemeSlider.setPaintTicks(true);
        greenSchemeSlider.setPaintLabels(false);
        greenSchemeSlider.setToolTipText("Green");
        greenSchemeSlider.setForeground(Color.GREEN);
        greenSchemeSlider.addChangeListener(this);
 
        // set the properties of the blue color shceme slider
        blueSchemeSlider.setBounds(430, 40, 50, 280);
        blueSchemeSlider.setMinorTickSpacing(COLOR_SLIDER_MINOR_TICK);
        blueSchemeSlider.setMajorTickSpacing(COLOR_SLIDER_MAJOR_TICK);
        blueSchemeSlider.setPaintTicks(true);
        blueSchemeSlider.setPaintLabels(false);
        blueSchemeSlider.setToolTipText("Blue");
        blueSchemeSlider.setForeground(Color.blue);
        blueSchemeSlider.addChangeListener(this);
 
        // set the color spot in the panel
        colorSpot.setText("Shape's Color.");
        colorSpot.setFont(new Font("Monospaced",Font.CENTER_BASELINE ,20));
        colorSpot.setBounds(320, 350, 260, 40);
        colorSpot.setAlignment(Label.CENTER);
        colorSpot.setForeground(new Color(255, 255, 255));
        colorSpot.setBackground(new Color(0, 0, 0));
 
        // show the labels
        windowPanel.add(widthLabel);
        windowPanel.add(heightLabel);
        windowPanel.add(pointXLabel);
        windowPanel.add(pointYLabel);
        windowPanel.add(redSchemeLabel);
        windowPanel.add(blueSchemeLabel);
        windowPanel.add(greenSchemeLabel);
 
        // show the sliders
        windowPanel.add(widthSlider);
        windowPanel.add(heightSlider);
        windowPanel.add(pointXSlider);
        windowPanel.add(pointYSlider);
        windowPanel.add(redSchemeSlider);
        windowPanel.add(blueSchemeSlider);
        windowPanel.add(greenSchemeSlider);
        windowPanel.add(colorSpot);
 
        windowPanel.add(button);
 
        windowPanel.setLayout(null);
        windowPanel.setDoubleBuffered(false);
 
        propertiesWindow.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        propertiesWindow.setSize(700, 450);
        propertiesWindow.setLocation(350, 200);
        propertiesWindow.setVisible(true);
        propertiesWindow.getContentPane().add(windowPanel);
    }
 
    public static void main(String[] args) {
 
        PropertiesWindow enhc = new PropertiesWindow();
 
        enhc.showPropertyWindow();
    }
 
    public void stateChanged(ChangeEvent event) {
 
            int width = widthSlider.getValue();
            int height = heightSlider.getValue();
            int pointX = pointXSlider.getValue();
            int pointY = pointYSlider.getValue();
            int red = redSchemeSlider.getValue();
            int green = greenSchemeSlider.getValue();
            int blue = blueSchemeSlider.getValue();
 
            if ((red >= 200) && (red <= 255)) {
 
                if ((green >= 200) && (green <= 255))  {
 
                    if ((blue >= 200) && (green <= 255)) {
 
                        colorSpot.setForeground(Color.BLACK);
                    }
                }
            }
            else if ((red <= 50) && (red >= 0)) {
 
                if ((green <= 50) && (green >= 0)) {
 
                    if ((blue <= 50) && (blue >= 0)) {
 
                        colorSpot.setForeground(Color.WHITE);
                    }
                }
            }
 
            // set the spot color according to the colors generated by sliders
            colorSpot.setBackground(new Color(red, green, blue));
    }
}

but with this code, the button appears perfectly.

package xxxGARBAGExxx;
 
import javax.swing.*;
import java.awt.*;
 
/**
 *
 * @author
 */
 
public class NewClass extends JFrame {
 
    JFrame frame;
    JButton button;
    JPanel panel;
 
    public void sample() {
 
        frame = new JFrame("Sample");
        panel = new JPanel();
        button = new JButton("My Button!");
 
        panel.add(button);
        frame.setDefaultCloseOperation(EXIT_ON_CLOSE); // is this a new class of the JFrame class?
        frame.setSize(500, 500);
        frame.setVisible(true);
        frame.getContentPane().add(panel);
 
    }
 
    public static void main(String[] args) {
 
        NewClass object = new NewClass();
 
        object.sample();
    }
}

The layout of your windowPanel is set to null, so your button is probably not being placed correctly until you set its bounds. I would encourage you to use layout managers (Using Layout Managers (The Java™ Tutorials > Creating a GUI With JFC/Swing > Laying Out Components Within a Container)), letting swing align and position things for you and having components position (or reposition) properly when windows are resized.