Jslider, not appearing on My frame

Question

im trying to make my slider appear on my gui once i run my java project, here is what i >have, any help would be nice :)

so the menu bar appears, the menu shapes appears, and the 3 shapes appear too, i just cant >get the slider to appear on at the bottom of the box

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class assignment

---

package assignment;

public class Assignment {

public static void main(String[] args) {
    
MyFrame pane = new MyFrame();  
   
pane.setVisible(true);
pane.setSize(400,400);

---

class MyFrame

---

package assignment;

import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;

public class MyFrame extends javax.swing.JFrame {

/**
 * Creates new form MyFrame
 */
public MyFrame() {
initComponents();
    
// Create the menu
JMenuBar topMenu = new JMenuBar();
this.setJMenuBar(topMenu);
    
//create the menu button "shapes"
JMenu shapes = new JMenu("Shapes");
topMenu.add(shapes);
//Create the 3 shapes for the menu
JMenuItem square = new JMenuItem("Square");
JMenuItem circle = new JMenuItem("Circle");        
JMenuItem triangle = new JMenuItem("Triangle");
    
//add shapes to menu
shapes.add(circle);
shapes.add(triangle);
shapes.add(square);
    
//add the menu
setJMenuBar(topMenu);
    
    
MyControlPanel pane = new MyControlPanel();
this.add(pane);
    
    
}

/**
 * This method is called from within the constructor to initialize the form.
 * WARNING: Do NOT modify this code. The content of this method is always
 * regenerated by the Form Editor.
 */
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {

    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
    getContentPane().setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 400, Short.MAX_VALUE)
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 300, Short.MAX_VALUE)
    );

    pack();
}// </editor-fold>

/**
 * @param args the command line arguments
 */
public static void main(String args[]) {
    /* Set the Nimbus look and feel */
    //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
    /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.

    try {
        for (javax.swing.UIManager.LookAndFeelInfo info :          javax.swing.UIManager.getInstalledLookAndFeels()) {
            if ("Nimbus".equals(info.getName())) {
                javax.swing.UIManager.setLookAndFeel(info.getClassName());
                break;
            }
        }
    } catch (ClassNotFoundException ex) {
        java.util.logging.Logger.getLogger(MyFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (InstantiationException ex) {
        java.util.logging.Logger.getLogger(MyFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (IllegalAccessException ex) {
        java.util.logging.Logger.getLogger(MyFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (javax.swing.UnsupportedLookAndFeelException ex) {
        java.util.logging.Logger.getLogger(MyFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    }
    //</editor-fold>

    /* Create and display the form */
    java.awt.EventQueue.invokeLater(new Runnable() {
        @Override
        public void run() {
        new MyFrame().setVisible(true);
        }
    });
    
    
}
// Variables declaration - do not modify
// End of variables declaration

}

---

class MyControlPanel

---

package assignment;

import javax.swing.JSlider;
import javax.swing.JTextField;


public class MyControlPanel extends javax.swing.JPanel {

/**
 * Creates new form MyControlPanel
 */
public MyControlPanel() {
initComponents();

JSlider slider = new JSlider();
slider.setMajorTickSpacing(10); 
slider.setPaintLabels(true); 
slider.setPaintTicks(true); 
 
JTextField boundary_length = new JTextField("Boundary Length");
JTextField area = new JTextField("Area");
    
 
this.add(slider);
this.add(area);
this.add(boundary_length);
    
}

/**
 * This method is called from within the constructor to initialize the form.
 * WARNING: Do NOT modify this code. The content of this method is always
 * regenerated by the Form Editor.
 */
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(this);
    this.setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 400, Short.MAX_VALUE)
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 300, Short.MAX_VALUE)
    );
}// </editor-fold>
// Variables declaration - do not modify
// End of variables declaration

}

Answer 1

What you're missing is an understanding of the GroupLayout

If I do this

public MyControlPanel() {
    initComponents();

    JSlider slider = new JSlider();
    slider.setMajorTickSpacing(10);
    slider.setPaintLabels(true);
    slider.setPaintTicks(true);

    JTextField boundary_length = new JTextField("Boundary Length");
    JTextField area = new JTextField("Area");

    setLayout(new FlowLayout());

    this.add(slider);
    this.add(area);
    this.add(boundary_length);

}

I get this...

All I did was change the layout manager to FlowLayout. No offense, but GroupLayout isn't suppose to be created by hand as is really suppose to be used with form editors.