PBO : Classes and Object ( A Deeper Look )
8.1 Introduction
Fig. 8.1 | Time1 class declaration maintains the time in 24-hour format.
8.2 Time Class Case Study
Fig. 8.2 | Time1 object used in an application.
8.3 Controlling Access to Members
Fig. 8.3 | Private members of class Time1 are not accessible.
8.4 Referring to the Current Object’s Members with the this Reference
Fig. 8.4 | this used implicitly and explicitly to refer to members of an object.
8.5 Time Class Case Study: Overloaded Constructors
Fig. 8.5 | Time2 class with overloaded constructors.
8.6
Fig. 8.6 | Overloaded constructors used to initialize Time2 objects.
Fig. 8.1 | Time1 class declaration maintains the time in 24-hour format.
/**
* Write a description of class Time1 here.
*
* @author (your name)
* @version (a version number or a date)
*/
// Fig. 8.1: Time1.java
// Time1 class declaration maintains the time in 24-hour format.
public class Time1
{
public int hour;
public int minute;
public int second;
public void setTime( int h, int m, int s )
{
if ( ( h >= 0 && h < 24 ) && ( m >= 0 && m < 60 ) &&
( s >= 0 && s < 60 ) )
{
hour = h;
minute = m;
second = s;
}
else
throw new IllegalArgumentException(
"hour, minute and/or second was out of range" );
}
public String toUniversalString()
{
return String.format( "%02d:%02d:%02d", hour, minute, second );
}
public String toString()
{
return String.format( "%d:%02d:%02d %s",
( ( hour == 0 || hour == 12 ) ? 12 : hour % 12 ),
minute, second, ( hour < 12 ? "AM" : "PM" ) );
}
}
Paste your text here. 8.2 Time Class Case Study
Fig. 8.2 | Time1 object used in an application.
/**
* Write a description of class Time1Test here.
*
* @author (your name)
* @version (a version number or a date)
*/
// Fig. 8.2: Time1Test.java
// Time1 object used in an application
public class Time1Test
{
public static void main( String[] args)
{
Time1 time = new Time1();
System.out.print( "The initial universal time is: ");
System.out.println( time.toUniversalString() );
System.out.print( "The initial standard time is: ");
System.out.println( time.toString() );
System.out.println();
time.setTime( 13, 27, 6);
System.out.print( "Universal time after setTime is: ");
System.out.println( time.toUniversalString() );
System.out.print( "Standard time after setTime is: ");
System.out.println( time.toString() );
System.out.println();
try
{
time.setTime( 99, 99, 99 );
}
catch ( IllegalArgumentException e)
{
System.out.printf( "Exception: %s\n\n", e.getMessage() );
}
System.out.println( "After attempting invalid settings:" );
System.out.print( "Universal time: ");
System.out.println( time.toUniversalString() );
System.out.print( "Standart time: ");
System.out.println( time.toString() );
}
}
8.3 Controlling Access to Members
Fig. 8.3 | Private members of class Time1 are not accessible.
/**
* Write a description of class MemberAccessTest here.
*
* @author (your name)
* @version (a version number or a date)
*/
// Fig. 8.3: MemberAccsessTest.java
// Private members of class Time1 are not accessible
public class MemberAccessTest
{
public static void main( String[] args)
{
Time1 time = new Time1();
time.hour = 7;
time.minute = 15;
time.second = 30;
}
}
8.4 Referring to the Current Object’s Members with the this Reference
Fig. 8.4 | this used implicitly and explicitly to refer to members of an object.
/**
* Write a description of class ThisTest here.
*
* @author (your name)
* @version (a version number or a date)
*/
// Fig. 8.4: ThisTest.java
// this used implicitly and explicitly to refer to members of an object.
public class ThisTest
{
public static void main( String[] args )
{
SimpleTime time = new SimpleTime(15, 30, 19);
System.out.println( time.buildString() );
}
}
class SimpleTime
{
public int hour;
public int minute;
public int second;
public SimpleTime( int hour, int minute, int second )
{
this.hour = hour;
this.minute = minute;
this.second = second;
}
public String buildString()
{
return String.format( "%24s: %s\n%24s: %s",
"this.toUniversalString()", this.toUniversalString(),
"toUniversalString()", toUniversalString() );
}
public String toUniversalString()
{
return String.format( "%02d: %02d :%02d",
this.hour, this.minute, this.second );
}
}
8.5 Time Class Case Study: Overloaded Constructors
Fig. 8.5 | Time2 class with overloaded constructors.
/**
* Write a description of class Time2 here.
*
* @author (your name)
* @version (a version number or a date)
*/
// Fig. 8.5: Time2.java
// Time2 class declaration with overloaded constructors.
public class Time2
{
public int hour;
public int minute;
public int second;
public Time2()
{
this( 0, 0, 0);
}
public Time2( int h )
{
this( h, 0, 0 );
}
public Time2( int h, int m )
{
this( h, m, 0 );
}
public Time2( int h, int m, int s )
{
setTime( h, m, s );
}
public Time2( Time2 time )
{
this( time.getHour(), time.getMinute(), time.getSecond() );
}
public void setTime( int h, int m, int s )
{
setHour( h );
setMinute( m );
setSecond( s );
}
public void setHour( int h )
{
if ( h >= 0 && h < 24 )
hour = h;
else
throw new IllegalArgumentException( "hour must be 0-23" );
}
public void setMinute( int m )
{
if ( m >= 0 && m < 60 )
minute = m;
else
throw new IllegalArgumentException( "minute must be 0-59" );
}
public void setSecond( int s )
{
if ( s >= 0 && s < 60 )
second = ( ( s >= 0 && s < 60 ) ? s : 0 );
else
throw new IllegalArgumentException( "second must be 0-59" );
}
public int getHour()
{
return hour;
}
public int getMinute()
{
return minute;
}
public int getSecond()
{
return second;
}
public String toUniversalString()
{
return String.format(
"%02d:%02d:%02d", getHour(), getMinute(), getSecond() );
}
public String toString()
{
return String.format( "%d:%02d:%02d %s",
( (getHour() == 0 || getHour() == 12) ? 12 : getHour() % 12 ),
getMinute(), getSecond(), getHour() < 12 ? "AM" : "PM" ) ;
}
}
8.6
Fig. 8.6 | Overloaded constructors used to initialize Time2 objects.
/**
* Write a description of class Time2Test here.
*
* @author (your name)
* @version (a version number or a date)
*/
// Fig. 8.6: Time2Test.java
// Overloaded constructors used to initialize Time2 objects.
public class Time2Test
{
public static void main(String[] args)
{
Time2 t1 = new Time2();
Time2 t2 = new Time2( 2 );
Time2 t3 = new Time2( 21, 34 );
Time2 t4 = new Time2( 12, 25, 42 );
Time2 t5 = new Time2( t4);
System.out.println( "Constructed with: ");
System.out.println( "tl: all arguments defaulted" );
System.out.printf( " %s\n", t1.toUniversalString() );
System.out.printf( " %s\n", t2.toString() );
System.out.println( " t2: hour spesified; minute and second defaulted" );
System.out.printf( " %s\n", t2.toUniversalString() );
System.out.printf( " %s\n", t2.toString() );
System.out.println( " t3: hour and minute spesified; second defaulted" );
System.out.printf( " %s\n", t3.toUniversalString() );
System.out.printf( " %s\n", t3.toString() );
System.out.println( " t4: hour, minute and second specified" );
System.out.printf( " %s\n", t4.toUniversalString() );
System.out.printf( " %s\n", t4.toString() );
System.out.println( " t5: Time2 object t4 specified" );
System.out.printf( " %s\n", t5.toUniversalString() );
System.out.printf( " %s\n", t5.toString() );
try
{
Time2 t6 = new Time2( 27, 74, 99 );
}
catch (IllegalArgumentException e )
{
System.out.printf( "\nException while initializing t6: %s\n", e.getMessage() );
}
}
}
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