import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.text.*;
import java.text.*;


public class Vhea extends Frame implements ActionListener{

    JFrame frame;
    JPanel panel1, panel2, panel3;
    JLabel inputLabel;
    JFormattedTextField inputField;
    JButton button;
    Container contentPane;
    JOptionPane optionPane;
    String inputTxt="";

     public static void main(String[] args) {
        Vhea tm = new Vhea();     

    }

    Vhea() {

        frame = new JFrame("Midterm in Compiler");
        panel1 = new JPanel();
        panel2 = new JPanel();
        panel3 = new JPanel();


        //InputField
        inputLabel = new JLabel("Input:");
        inputField = new JFormattedTextField();
        inputField.setValue(inputTxt);
        inputField.setColumns(10);


        //Scan button 
        button = new JButton("SCAN");
        button.setActionCommand("scan");
        button.addActionListener(this);

        //Pack
        contentPane = frame.getContentPane();
        panel1.add(inputLabel);
        panel1.add(inputField);

        panel1.setBackground(Color.pink);
        panel1.add(button);
        panel2.setBackground(Color.pink);
        panel3.setBackground(Color.pink);


     contentPane.add(panel2, BorderLayout.NORTH);
     contentPane.add(panel1, BorderLayout.CENTER);   
     contentPane.add(panel3, BorderLayout.SOUTH);

        frame.setSize(300, 100);
        frame.setVisible(true);
        frame.setLocationRelativeTo(null); 
        frame.setResizable(false);}



    public void actionPerformed(ActionEvent ae) {
        String s = ae.getActionCommand();
        String wordInput=" ";
        String msg1=" is a INVALID input";
        String msg2=" is a VALID input";
        if (s.equals("scan")) {
            wordInput=((String)inputField.getValue());
            int i=0;
     while(i < wordInput.length()){
         char a = wordInput.charAt(i);
         if (i == 0){
            if( a == '$'){
              }
            else{
                 i=wordInput.length();
                JOptionPane.showMessageDialog(null,wordInput + msg1);
                 inputField.setValue("");}}
         else if (i == 1){
                if(Character.isLetter(a) == true){
                }
                else{
                i=wordInput.length();
               JOptionPane.showMessageDialog(null,wordInput + msg1);
               inputField.setValue("");}}
         else{
             if(Character.isLetter(a) == true || Character.isDigit(a)== true || a == '_' || a == ' ' ){
               }
             else{
             i=wordInput.length();
            JOptionPane.showMessageDialog(null,wordInput + msg1);
            inputField.setValue("");}}
         i++;}

         if (i ==wordInput.length()){
         JOptionPane.showMessageDialog(null,wordInput + msg2);
         inputField.setValue("");}
    }



        } 
    }

... pls help... i cant use ImageIcon..

 ImageIcon icon = createImageIcon("bflowers.jpg");

Edited 3 Years Ago by Nick Evan: Fixed formatting

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