8.1 Introduction
8.2 Time Class Study
/**
* Fig. 8.1: Time1.java
* Time1 class declaration maintains the time in 24-hour format.
* Fakhriyah 5115100126
*/
public class Time1
{
private int hour; // 0 - 23
private int minute; // 0 - 59
private int second; // 0 - 59
//set a new time value using universal time; throw an
// exception if the hour, minute or second is invalid
public void setTime( int h, int m, int s )
{
//validate hour, minute and second
if ( ( h >= 0 && h < 24 ) && ( m >= 0 &&m < 60) &&
( s >= 0 && s < 60 ) )
{
hour = h;
minute = m;
second = s;
} // end if
else
throw new IllegalArgumentException(
"hour, minute and/or second was out of range" );
} //end method setTime
// convert to String in universal-time format (HH:MM:SS)
public String toUniversalString()
{
return String.format( "%02d:%02d:%02d", hour, minute, second );
} // end method toUniversalString
//convert to String in standard-time format (H:MM:SS AM or PM)
public String toString()
{
return String.format( "%d:%02d:%02d %s",
( ( hour == 0 || hour == 12 ) ? 12 : hour % 12 ),
minute, second, ( hour < 12 ? "AM" : "PM" ) );
} //end method toString
} // end class Time1
/**
* Fig. 8.2: Time1Test.java
* Time1 objct used in an application.
* Fakhriyah 5115100126
*/
public class Time1Test
{
public static void main ( String[] args )
{
// creat and initializa a Time1 object
Time1 time = new Time1(); // invokes Time1 constructor
// output string representations of the time
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(); // output a blank line
// change time and output updated time
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: " );
System.out.println( time.toString() );
System.out.println(); // output a blank line
// attempt to set time with invalid values
try
{
time.setTime( 99, 99, 99 ); // all values out of range
} // end try
catch ( IllegalArgumentException e )
{
System.out.printf( "Exception: %s\n\n", e.getMessage() );
} // end catch
// display time after attempt to set invalid values
System.out.println( "After attempt invalid settings:" );
System.out.print( "Universal time: " );
System.out.println( time.toUniversalString() );
System.out.print( "Standard time: " );
System.out.println( time.toString() );
} // end main
} // end class Time1Test
Outputnya:
8.3 Controlling Access to Members
/**
* Fig. 8.3: MemberAccessTest.java
* Private members of class Time1 are not accessible.
* Fakhriyah 5115100126
*/
public class MemberAccessTest
{
public static void main( String[] args )
{
Time1 time = new Time1(); // create and initialize Time1 object
time.hour = 7; // error: hour has private access in Time1
time.minute = 15; // error: minute has private access in Time1
time.second = 30; // error: second has private access in Time1
} // end main
} // end class MemberAccessTest
8.4 Referring to the Current Object's Members with the this Reference
/**
* Fig. 8.4: ThisTest.java
* this used implicity and explicity to refer to members of an object.
* Fakhriyah 5115100126
*/
public class ThisTest
{
public static void main( String[] args)
{
SimpleTime time = new SimpleTime( 15, 30, 19 );
System.out.println( time.buildString() );
} // end main
} // end class ThisTest
// class SimpleTime demonstrates the "this" reference
class SimpleTime
{
private int hour; // 0-23
private int minute; // 0-59
private int second; // 0-59
// if the construction uses parameter names identical to
// instance variable names the "this" reference is
// required to distinguish between the 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
} // end SimpleTime constructor
// use explicit and implicit "this to call toUniversalString
public String buildString()
{
return String.format( "%24s: %s\n%24s: %s",
"this.toUniversalString()", this.toUniversalString(),
"toUniversalString()", toUniversalString() );
} // end method buildString
// convert to String in universal-time format (HH:MM:SS)
public String toUniversalString()
{
// "this" is not required here to access instance variables,
// because method does not have local variables with same
// name as instance variables
return String.format( "%02d:%02d:%02d",
this.hour, this.minute, this.second );
} // end method toUniversalString
} // end class SimpleTime
Outputnya:
8.5 Time Class Case Study: Overloaded Constructions
/**
* Fig. 8.5: Time2.java
* TIme2 class declaration with overloaded constructors.
* Fakhriyah 5115100126
*/
public class Time2
{
private int hour; // 0 - 23
private int minute; // 0 - 59
private int second; // 0 -59
// Time2 no-argument constructor:
// initializes each instance variable to zero
public Time2()
{
this( 0, 0, 0); // invoke Time2 constructor with three arguments
} // end Time2 no-argument constructor
// Time2 constructor: hour supplied, minute and second defaulted to 0
public Time2( int h )
{
this( h, 0, 0 ); // invoke Time2 constructor with three arguments
} // end Time2 one-argument constructor
// Time2 constructor: hour and minute supplied, second defaulted to 0
public Time2( int h, int m )
{
this( h, m, 0 ); // invoke Time2 constructor with three arguments
} // end Time2 two-argument constructor
// Time2 constructor: hour, minute and second supplied
public Time2( int h, int m, int s )
{
setTime( h, m, s ); // invoke setTime to validate time
} // end Time2 three-argument constructor
// Time2 constructor: another Time2 object supplied
public Time2( Time2 time )
{
// invoke Time2 three-argument constructor
this( time.getHour(), time.getMinute(), time.getSecond() );
} // end Time2 constructor with a Time2 object argument
// Set Methods
// set a new time value using universal time;
// validate the data
public void setTime( int h, int m, int s )
{
setHour( h ); // set the hour
setMinute( m ); // set the minute
setSecond( s ); // set the second
} // end method setTime
// validate and set hour
public void setHour( int h )
{
if( h >= 0 && h < 24 )
hour = h;
else
throw new IllegalArgumentException( "hour must be 0-23" );
} // end method setHour
// validate and set minute
public void setMinute( int m )
{
if( m >= 0 && m < 60 )
minute = m;
else
throw new IllegalArgumentException( "minute must be 0-59" );
} // end method setMinute
// validate and set second
public void setSecond( int s )
{
if( s >= 0 && s < 60 )
second = s;
else
throw new IllegalArgumentException( "second must be 0-59" );
} // end method setSecond
// Get Methods
// get hour value
public int getHour()
{
return hour;
} // end method getHour
// get minute value
public int getMinute()
{
return minute;
} // end method getMinute
// get second value
public int getSecond()
{
return second;
} // end method getSecond
// convert to String in universal-time format (HH:MM:SS)
public String toUniversalString()
{
return String.format( "%02d:%02d:%02d", getHour(), getMinute(), getSecond() );
} // end method toUniversalString
//convert to String in standard-time format (H:MM:SS AM or PM)
public String toString()
{
return String.format( "%d:%02d:%02d %s",
( (getHour() == 0 || getHour() == 12) ? 12 : getHour() % 12), getMinute(), getSecond(),
( getHour() < 12 ? "AM" : "PM" ) );
} // end method toString
} // end class Time2
/**
* Fig. 8.6: Time2Test.java
* Overloaded constructors used to initialized Time2Objects.
* Fakhriyah 5115100126
*/
public class Time2Test
{
public static void main( String[] args )
{
Time2 t1 = new Time2(); // 00:00:00
Time2 t2 = new Time2( 2 ); // 02:00:00
Time2 t3 = new Time2( 21, 34 ); // 21:34:00
Time2 t4 = new Time2( 12, 25, 42 ); // 12:25:42
Time2 t5 = new Time2( t4 ); // 12:25:42
System.out.println( "Constructed with:" );
System.out.println( "t1: all arguments defaulted" );
System.out.printf( " %s\n", t1.toUniversalString() );
System.out.printf( " %s\n", t1.toString() );
System.out.println( "t2: hour specified; 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 specified; 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() );
// attempt to initialize t6 with invalid values
try
{
Time2 t6 = new Time2( 27, 74, 99 ); // invalid values
} // end try
catch ( IllegalArgumentException e )
{
System.out.printf( "\nException while initializing t6: %s\n", e.getMessage() );
} // end catch
} // end main
} // end class Time2Test
8.6 Default and No-Argument Constructor
8.7 Notes on Sets and Gets Methods
8.8 Composition
/**
* Fig. 8.7: Date.java
* Date class declaration.
* Fakhriyah 5115100126
*/
public class Date
{
private int month; // 1-12
private int day; // 1-31 based on month
private int year; // any year
private static final int[] daysPerMonth = // days in each month
{ 0, 31, 28, 31, 30, 31, 30, 31, 30, 31, 30, 31 };
// constructor: call checkMonth to confirm proper value for month;
// call checkDay to confirm proper value for day
public Date( int theMonth, int theDay, int theYear )
{
month = checkMonth( theMonth ); // validate month
year = theYear; // could validate year
day = checkDay( theDay ); // validate day
System.out.printf( "Date object constructor for date %s\n", this );
} // end Date constructor
// utility method to confirm proper month value
private int checkMonth( int testMonth )
{
if ( testMonth > 0 && testMonth <= 12 ) // validate month
return testMonth;
else // month is invalid
throw new IllegalArgumentException( "month must be 1-12" );
} // end method checkMonth
// utility method to confirm proper day value based on month and year
private int checkDay( int testDay )
{
// check if day in range for month
if ( testDay > 0 && testDay <= daysPerMonth[ month ] )
return testDay;
// check for leap year
if ( month == 2 && testDay == 29 && ( year % 400 == 0 ||
( year % 4 == 0 && year % 100!= 0 ) ) )
return testDay;
throw new IllegalArgumentException( "day out-of-range for the specified month and year" );
} // end method checkDay
// return a String of the form month/day/year
public String toString()
{
return String.format( "%d/%d/%d", month, day, year );
} // end method toString
} // end class Date
/**
* Fig. 8.8: Employee.java
* Employee class with references to other objects.
* Fakhriyah 5115100126
*/
public class Employee
{
private String firstName;
private String lastName;
private Date birthDate;
private Date hireDate;
// constructor to initialize name, birth day and hire date
public Employee( String first, String last, Date dateOfBirth, Date dateOfHire )
{
firstName = first;
lastName = last;
birthDate = dateOfBirth;
hireDate = dateOfHire;
} // end Employee constructor
// convert Employee to String format
public String toString()
{
return String.format( "%s, %s Hired: %s Birthday: %s",
lastName, firstName, hireDate, birthDate );
} // end method toString
} // end class Employee
/**
* Fig. 8.9: EmployeeTest.java
* Composition demonstration.
* Fakhriyah 5115100126
*/
public class EmployeeTest
{
public static void main( String[] args )
{
Date birth = new Date( 7, 24, 1949 );
Date hire = new Date( 3, 12, 1988 );
Employee employee = new Employee( "Bob", "Blue", birth, hire );
System.out.println( employee );
} // end main
} // end class EmployeeTest
