define -> create -> use -> destroy -> redefined

// Fig. 8.1: Time1.java
// Time1 class declaration maintains the time in 24-hour format.
import java.text.DecimalFormat; 

public class Time1 extends Object {
   private int hour;     // 0 - 23
   private int minute;   // 0 - 59
   private int second;   // 0 - 59

   // Time1 constructor initializes each instance variable to zero; 
   // ensures that each Time1 object starts in a consistent state
   public Time1()
   {
      setTime( 0, 0, 0 );
   }

   // set a new time value using universal time; perform 
   // validity checks on the data; set invalid values to zero
   public void setTime( int h, int m, int s )
   {
      hour = ( ( h >= 0 && h < 24 ) ? h : 0 );
      minute = ( ( m >= 0 && m < 60 ) ? m : 0 );
      second = ( ( s >= 0 && s < 60 ) ? s : 0 );
   }

   // convert to String in universal-time format
   public String toUniversalString()
   {
      DecimalFormat twoDigits = new DecimalFormat( "00" );

      return twoDigits.format( hour ) + ":" +
         twoDigits.format( minute ) + ":" + twoDigits.format( second );
   }

   // convert to String in standard-time format
   public String toStandardString()
   {
      DecimalFormat twoDigits = new DecimalFormat( "00" );
      
      return ( (hour == 12 || hour == 0) ? 12 : hour % 12 ) + ":" + 
         twoDigits.format( minute ) + ":" + twoDigits.format( second ) +
         ( hour < 12 ? " AM" : " PM" );
   }

} // end class Time1

// Fig. 8.2: TimeTest1.java
// Class TimeTest1 to exercise class Time1.
import javax.swing.JOptionPane;

public class TimeTest1 {

   public static void main( String args[] )
   {
      Time1 time = new Time1();  // calls Time1 constructor

      // append String version of time to String output
      String output = "The initial universal time is: " +
         time.toUniversalString() + "\nThe initial standard time is: " +
         time.toStandardString();

      // change time and append updated time to output
      time.setTime( 13, 27, 6 ); 
      output += "\n\nUniversal time after setTime is: " + 
         time.toUniversalString() +
         "\nStandard time after setTime is: " + time.toStandardString();

      // set time with invalid values; append updated time to output
      time.setTime( 99, 99, 99 ); 
      output += "\n\nAfter attempting invalid settings: " + 
         "\nUniversal time: " + time.toUniversalString() +
         "\nStandard time: " + time.toStandardString();

      JOptionPane.showMessageDialog( null, output,
         "Testing Class Time1", JOptionPane.INFORMATION_MESSAGE );

      System.exit( 0 );

   } // end main

} // end class TimeTest1

// Fig. 8.3: TimeTest2.java
// Errors resulting from attempts to access private members of Time1.
public class TimeTest2 {

   public static void main( String args[] )
   {
      Time1 time = new Time1();

      time.hour = 7;    // error: hour is a private instance variable
      time.minute = 15; // error: minute is a private instance variable
      time.second = 30; // error: second is a private instance variable
   }

} // end class TimeTest2