Better Design Pattern For Terminal-Like GUI

Question

I am working on a java swing project that looks like a Terminal (but with less functionality).

The GUI contains a jTextArea to display output and a jTextField for user input.

Here is an application of the my GUI to perform a simple task.

1. Ask the user to enter a number.
2. If successful, ask the user to enter a smaller
3. If successful, prompt out the text "done!".

Is there a better way to do this other than state machine?

Here is the code:

package com.TerminalPanelGUI;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class TerminalPanel extends javax.swing.JPanel
{
 private int state;
 /**
 * Creates a new Terminal Panel
 */
 public TerminalPanel()
 {
 state = 0;
 initComponents();
 textArea.setText("Enter a number: \n");
 textField.addActionListener(new ActionListener()
 {
 @Override
 public void actionPerformed(ActionEvent ae)
 {
 System.out.println("In action performed: state is " + state);
 switch(state)
 {
 case 0:
 State0();
 break;
 case 1:
 State1();
 break;
 }
 }
 });
 }
 private int dummy;
 private void State0()
 {
 try
 {
 dummy = Integer.parseInt(textField.getText());
 state = 1;
 //prompt for next state
 textArea.append("Enter a smaller number: \n");
 }
 catch(NumberFormatException e)
 {
 textArea.append("Invalid entry. Try again \n");
 state = 0;
 }
 }
 private void State1()
 {
 try
 {
 if(Integer.parseInt(textField.getText()) < dummy)
 {
 state = 2;
 //prompt for next state
 textArea.append("done!");
 }
 else
 {
 state = 1;
 //prompt for next state
 textArea.append("Enter a smaller number: \n");
 }
 }
 catch(NumberFormatException e)
 {
 textArea.append("Invalid entry. Try again \n");
 }
 }
 /**
 * 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() {
 scrollPane = new javax.swing.JScrollPane();
 textArea = new javax.swing.JTextArea();
 textField = new javax.swing.JTextField();
 setLayout(new org.netbeans.lib.awtextra.AbsoluteLayout());
 textArea.setEditable(false);
 textArea.setColumns(20);
 textArea.setRows(5);
 scrollPane.setViewportView(textArea);
 add(scrollPane, new org.netbeans.lib.awtextra.AbsoluteConstraints(0, 0, 400, 250));
 add(textField, new org.netbeans.lib.awtextra.AbsoluteConstraints(0, 270, 400, 30));
 }// </editor-fold> 
 // Variables declaration - do not modify 
 private javax.swing.JScrollPane scrollPane;
 protected javax.swing.JTextArea textArea;
 protected javax.swing.JTextField textField;
 // End of variables declaration 
}

Answer 1

Maybe something like this? Note: may add textField as a member of State0 and State1

public interface State
{
 boolean hasNext();
 State next();
}
public final class State0
 implements State
{
 private boolean okToContinue = false;
 private int number;
 @Override
 public boolean hasNext()
 {
 try {
 textArea.append("Enter a number");
 number = Integer.parseInt(textField.getText());
 okToContinue = true;
 } catch (NumberFormatException ignored) {
 textArea.append("Input is not a number");
 }
 return true;
 }
 @Override
 public State next()
 {
 return okToContinue ? new State1(number) : this;
 }
}

The State1 implementation is then obvious. In the main loop you can just do:

State state = new State0();
while (state.hasNext())
 state = state.next();