import java.awt.*;
import java.awt.event.*;

class EnvarJni extends Frame implements ActionListener {
  public native String getEnvar(String varname);     //JNI native method declaration

    TextArea ta = new TextArea (5, 70);
    Button startbutton = new Button("Get Envar") ;
    Button clearbutton = new Button("CLEAR") ;
    TextField  tf = new TextField(15) ;

EnvarJni() {        //constructor
     this.setLayout(new BorderLayout(10,10));
     Panel p1 = new Panel() ; 
     this.setBackground(new Color(192, 192, 192)) ;
      p1.add(new Label("Variable Name:", Label.RIGHT)) ;
      p1.add(tf);
      p1.add(startbutton);
      p1.add(clearbutton);
      startbutton.setBackground(Color.red) ;
      startbutton.addActionListener(this) ;
      clearbutton.addActionListener(this) ;
      add(p1, BorderLayout.NORTH) ;
      add(ta,  BorderLayout.CENTER) ;

    this.addWindowListener(new WindowAdapter() { public void
         windowClosing(WindowEvent e) { System.exit(0); } } );
  }

  public void actionPerformed(ActionEvent evt) {
   if(evt.getSource() == clearbutton) {
     ta.setText("");
     tf.setText("");
    }
     if( evt.getSource() == startbutton ) {
       if(tf.getText().trim().length() ==0)       //if only white space
	return;
      String envarval = this.getEnvar(tf.getText().trim()) ;
      ta.append(envarval + "\n") ;
    }
  }

  public static void main(String args[]) {
      EnvarJni vj = new EnvarJni();
      vj.pack();
      vj.show();
  }

  static {
    System.loadLibrary("envarjni");
  }

}