// Fig. 8.4: ThisTest.java
// Using the this reference to refer to fields and methods.
import javax.swing.*;
import java.text.DecimalFormat;

public class ThisTest {

   public static void main( String args[] )
   {
      SimpleTime time = new SimpleTime( 12, 30, 19 );

      JOptionPane.showMessageDialog( null, time.buildString(),
         "Demonstrating the \"this\" Reference",
         JOptionPane.INFORMATION_MESSAGE );

      System.exit( 0 );
   }

} // end class ThisTest

// class SimpleTime demonstrates the "this" reference
class SimpleTime {
   private int hour;
   private int minute;
   private int second;   

   // constructor uses parameter names identical to instance variable
   // names; "this" reference required to distinguish between names
   public SimpleTime( int hour, int minute, int second )
   {
      this.hour = hour;      // set "this" object's hour
      this.minute = minute;  // set "this" object's minute
      this.second = second;  // set "this" object's second
   }

   // use explicit and implicit "this" to call toStandardString
   public String buildString()
   {
      return "this.toStandardString(): " + this.toStandardString() +
         "\ntoStandardString(): " + toStandardString();
   }

   // return String representation of SimpleTime
   public String toStandardString()
   {
      DecimalFormat twoDigits = new DecimalFormat( "00" );
      
      // "this" is not required here, because method does not 
      // have local variables with same names as instance variables
      return twoDigits.format( this.hour ) + ":" +
         twoDigits.format( this.minute ) + ":" +
         twoDigits.format( this.second );
   }

} // end class SimpleTime