// Fig. 8.4: ThisTest.java
// Using the this reference to refer to instance variables 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