Question

thanks for looking at this for me, heres my problems:

My If statement in my MyFrame class is saying “MyShape is abstract, cannot be instantiated”
i also do not know how to complete my actionlistener so that it creates a instance of the shape i chose from the jmenu. and lastly sets the dimension of my Jslider to the size and area of my sqaure and adds it to a JtextField.

1. how do i fix the error “MyShape is abstract, cannot be instantiated” ?
2. any tips on how to complete my if statement so that the shape i select is linked to my Jslider so it value is added to that shape ie a square or circle class?
3. how do i then out put the 2 methods on finding the legth and area of that class ie the square or circle to 2 Jtext fields?

I would love any help you can throw my way, if you can please explain what i need to do it a easy way for a noob at programming like me could understand 🙂

---

MyFrame

---

    package assignment;

    import java.awt.event.ActionEvent;
    import java.awt.event.ActionListener;
    import javax.swing.JMenu;
    import javax.swing.JMenuBar;
    import javax.swing.JMenuItem;


    public class MyFrame extends javax.swing.JFrame {


    public MyFrame() {


    // 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);
    }

    @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.
     * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
     */
    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() {
        public void run() {
            new MyFrame().setVisible(true);
        }
    });

    class squareAction implements ActionListener {

        public void actionPerformed(ActionEvent e) {

            JMenuItem clickedMenu = (JMenuItem) e.getSource();
            if (clickedMenu.getText().equals("Square")) {
                MyShape ASquare = new MyShape() {
                };
            } else if (clickedMenu.getText().equals("Circle")) {
                MyShape Circle = new MyShape();
            } else if (clickedMenu.getText().equals("Triangle")) {
                MyShape Triangle = new MyShape();
            }
        }
    }
    }
    }

---

Jpanel – MyControlPanel

    package assignment;

    //import java.awt.FlowLayout;
    import java.awt.BorderLayout;
    import java.awt.FlowLayout;
    import javax.swing.GroupLayout;
    import javax.swing.GroupLayout.Alignment;
    import javax.swing.JLabel;
    import javax.swing.JPanel;
    import javax.swing.JSlider;
    import javax.swing.JTextField;
    import javax.swing.event.ChangeEvent;
    import javax.swing.event.ChangeListener;

    public class MyControlPanel extends javax.swing.JPanel {

JSlider slider;
JLabel sliderLabel;
JLabel sliderdimension;
JLabel blank;
JLabel dl;
JLabel area1;

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


    slider = new JSlider();
    slider.setValue(50);
    slider.addChangeListener(new MyChangeAction());
    slider.setMajorTickSpacing(10);
    slider.setPaintLabels(true);
    slider.setPaintTicks(true);
    slider.setBounds(300, 50, 100, 50);

    sliderLabel = new JLabel("50");
    blank = new JLabel("     ");
    sliderdimension = new JLabel("Shape Dimension:");

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

    dl = new JLabel("Boundary Length =");
    area1 = new JLabel("Area =");

    setLayout(new BorderLayout());


    JPanel sliderPanel = new JPanel();
    sliderPanel.setLayout(new FlowLayout(FlowLayout.CENTER, 10, 0));


    sliderPanel.add(sliderdimension);
    sliderPanel.add(sliderLabel);
    sliderPanel.add(slider);
    sliderPanel.add(dl);
    sliderPanel.add(boundary_length);
    sliderPanel.add(area1);
    sliderPanel.add(area);
    this.add(sliderPanel, BorderLayout.PAGE_END);



}

/**
 * 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.
 */
// <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                   

public class MyChangeAction implements ChangeListener {

    //complete code here
    public void stateChanged(ChangeEvent ce) {
        int value = slider.getValue();
        String str = Integer.toString(value);
        sliderLabel.setText(str);


    }
    } // end class
    }

---

MyShape

---

    package assignment;

    public abstract class MyShape
 {

double thelength;
double thearea;



public abstract double computeBoundaryLength(double Length);

public abstract double computeArea (double Length);
 }

---

ASquare

---

    package assignment;

    public class ASquare extends MyShape {

@Override
public double computeBoundaryLength(double Length) 
{
    thelength=(4*Length);
    return thelength;
}

@Override
public double computeArea(double Length) 
{
    thearea=(Length*Length);
    return thearea;
}

}

---

class shapeAction implements ActionListener{
public void actionPerformed(ActionEvent e){

            JMenuItem clickedMenu = (JMenuItem)e.getSource();
            if (clickedMenu.getText().equals("Square")){
                 //implement abstract methods
            MyShape ASquare = new ASquare();  
            ASquare.addActionListener(new shapeAction());
            }
            else if (clickedMenu.getText().equals("Circle")){ 
                 //implement abstract methods
                MyShape ACircle = new ACircle();
            ACircle.addActionListener(new shapeAction());
            }
            else if (clickedMenu.getText().equals("Triangle")){ 
                 //implement abstract methods
                MyShape ATriangle = new ATriangle();
            ATriangle.addActionListener(new shapeAction());   

Answer 1

• Your squareAction is meant to be the class that listens to all the possible menu selections (one for each kind of shape), so it shoud be named ShapeMenuAction or something like that. If you want ShapeMenuAction‘s actionPerformed to be executed when a menu option is selected, you have create one instance of it and add it to each MenuItem with addActionListener method on them. Otherwise, nothing will happen.

In MyFrame:

JMenuItem square = new JMenuItem("Square");
square.addActionListener(new ShapeAction());
JMenuItem circle = new JMenuItem("Circle");
circle.addActionListener(new ShapeAction());
JMenuItem triangle = new JMenuItem("Triangle");
triangle.addActionListener(new ShapeAction());

• Inside your actionPerformed you have to instantiate a concrete subclass of MyShape. Now you are doing nothing but instantiating a shape, you have to do something with the object before the method ends, right?. Create a setShape method in your MyControlPanel and call it from actionPerformed, passing the newly created shape to it.

In ShapeAction:

    public void actionPerformed(ActionEvent e) {
       JMenuItem clickedMenu = (JMenuItem) e.getSource();
       if (clickedMenu.getText().equals("Square")) {
           MyShape aSquare = new ASquare();
           myControlPanel.setShape(aSquare);
       } else if (clickedMenu.getText().equals("Circle")) {
           MyShape aCircle = new ACircle();
           myControlPanel.setShape(aCircle);             
       } else if (clickedMenu.getText().equals("Triangle")) {                 
           MyShape aTriangle = new MyShape();  
           myControlPanel.setShape(aTriangle);           
       }         
    } 

You have to create a MyControPanel named myControlPanel in MyFrame:

private MyControlPanel myControlPanel

and add it with

myControlPanel = new MyControlPanel();
getContentPane().add(myControlPanel);

before

pack();

• In MyControlPanel now you can update your labels according to the slider value and the selected shape, everytime one of them changes.

  private MyShape shape;
  public void set Shape(MyShape shape) {
  this.shape = shape;
  updateLabels();
  }