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

public class JavaCommentsChecker extends JFrame implements ActionListener{
    private Font demoFont;
    private JTextArea commentsArea;
    private JLabel resultLabel;
    private JButton actionButton;
    private String comments;
    private LinkedList<Character> s;
    private boolean finalStateReached = false;
    
    public JavaCommentsChecker(){
      super( "Multiple-line Comment Syntax Checker" );
         
         demoFont = new Font(Font.SANS_SERIF, Font.BOLD, 20);
         Container container = getContentPane();
         container.setLayout( new FlowLayout() );
      
         commentsArea = new JTextArea("/*** Please type your comments here. ***/");
         commentsArea.setRows(10);
         commentsArea.setColumns(20);
         commentsArea.setLineWrap(true);
         commentsArea.setFont(demoFont);
         container.add( commentsArea );
         
         resultLabel = new JLabel("                                ");
         resultLabel.setOpaque(true);
         resultLabel.setBackground(Color.yellow);
         resultLabel.setFont(demoFont);
         container.add( resultLabel );
      
         actionButton = new JButton( "Check Comments Syntax" );
         actionButton.setFont(demoFont);
         container.add( actionButton );
         actionButton.addActionListener( this );
         
         setSize( 460, 400 );
         setVisible( true );
    }
    
    public void actionPerformed( ActionEvent event ){
         String comments = commentsArea.getText();
         s = new LinkedList<Character>();
         for(int i=0; i<comments.length(); i++)
            s.add(comments.charAt(i));
         if(FSM())
            resultLabel.setText("Valid Multiple-line Comments.");
         else
            resultLabel.setText("Invalid Multiple-line Comments.");
    }
    
    private boolean FSM(){ //Character = char. Java does the conversion.
        finalStateReached=false;
        if(s.remove()=='/'&&s.remove()=='*'){  //states A and B coded here.
            stateC();
            return finalStateReached && s.isEmpty();
        }
        else
            return false;
    }
    
    private void stateC(){
        while(!s.isEmpty() && s.remove()!='*'){
        }
        stateD();
    }
    
    private void stateD(){
        while(!finalStateReached && !s.isEmpty()){
            char c = s.remove();
            if(c=='/')
                finalStateReached = true;   
            else if(c=='*')
                stateD();
            else
                stateC();
        }
    }
    
    public static void main(String args[]){ 
        new JavaCommentsChecker(); 
    }
}