Object, Class, Message and Method JAVA

Object, Class, Message and Method

In object-oriented programming, a class is a template for structure definition and object creation. So the object of an instance of a class, that class is a collection of plans that specify how to build an object.

Object and Class

Information-related information and describes an object called object attributes (object attribute). This attribute allows an object has a value attribute that stands alone. Besides object attributes also have an action called by the method. So the method is a set of operations on an object in the form of code instructions.

General syntax format-making class is as follows:

class classname {
// declare instance variables var1 type;
var2 type;
// ... type varN;
// declare methods
type method1 (parameters) {
// body of method
}
type method2 (parameters) {
// body of method
}
// ...
type methodN (parameters) {
// body of method
}
}

Defining Class

Consider the example of a class definition of vehicles consisting of three instance variables and the making of objects of that class, such as vehicle class pembuaan below:

1	public class Vehicle {

2	int passenger; // number of people in the vehicle

3	int capacity_bb; // fuel capacity

4	int mpg; // consumption of miles per gallon of fuel

5

}

Creating Objects

Objects created by the pre-defined class that is a class above the previous vehicle. 
so coding for the object as follows:

01	public class VehicleObjects {

02	public static void main (String [] args) {

03	Vehicle minivan = new Vehicle ();

04	Vehicle sportscar = new Vehicle ();

05	int range1, range2;

06	minivan.passenger = 7;

07	minivan.capacity_bb = 16;

08	minivan.mpg = 21;

09	sportscar.passenger = 2;

10	sportscar.capacity_bb = 14;

11	sportscar.mpg = 12;

12	range1 = minivan. capacity_bb * minivan.mpg;

13	range2 = sportscar. capacity_bb * sportscar.mpg;

14	System.out.println ("Minivan can carry "

15	+ minivan. passenger + " person with range " + range1);

16	System.out.println ("Sportscar can bring "

17	+ sportscar. passenger + " person with range " + range2);

18

}

19

}

coding results

Adding Method into Class

Class that has been made over there just an instance variable, now add some operation (method) into the class.

vehicle class with the method:

01	public class Vehicle {

02	int passenger; // number of people in the vehicle

03	int capacity_bb; // fuel capacity

04	int mpg; // consumption of miles per gallon of fuel

05	String name = new String ();

06	int getRange () {

07	return mpg*capacity_bb;

08

}

09	double getNumBB (int miles) {// amount of fuel needs

10	return (double) miles / mpg;

11

}

12

}

objekvehicle class with the method:

01	public class VehicleObjects {

02	public static void main (String [] args) {

03	Vehicle minivan = new Vehicle ();

04	Vehicle sportscar = new Vehicle ();

05	double gallon;

06	int distance = 259;

07	minivan.name = "Minivan";

08	minivan.passenger = 7;

09	minivan.capacity_bb = 16;

10	minivan.mpg = 21;

11	sportscar.name = "Sportscar";

12	sportscar.passenger = 2;

13	sportscar.capacity_bb = 14;

14	sportscar.mpg = 12;

15	gallon = minivan.getNumBB (distance);

16	System.out.println (minivan.name + " requires " + gallon +

17	" gallons to travel distance " + distance + " miles.");

18	gallon = sportscar.getNumBB (distance);

19	System.out.println (sportscar.name + " requires " + gallon +

20	" gallons to travel distance " + distance + " miles.");

21

}

22

}

coding results

constructor

A constructor is an object initialization when it is created.  Constructor name equal to the name of its class. 

vehicle class with a constructor:

01	public class Vehicle {

02	int passenger; // number of people in the vehicle

03	int capacity_bb; // fuel capacity

04	int mpg; // consumption of miles per gallon of fuel

05	String name = new String ();

06	Vehicle (String name, int passenger, int capacity, int mpg) {

07	this.name = name;

08	this.passenger = passenger;

09	this.capacity_bb = capacity;

10	this.mpg = mpg;

11

}

12	int getRange () {

13	return mpg * capacity_bb;

14

}

15	double getNumBB (int miles) {// amount of fuel needs

16	return (double) miles / mpg;

17

}

18

}

objekvehicle class with a constructor:

01	public class VehicleObjects {

02	public static void main (String [] args) {

03	Vehicle minivan = new Vehicle ("Minivan", 7,16,21);

04	Vehicle sportscar = new Vehicle ("Sportscar", 2,14,12);

05	double gallon;

06	int distance = 259;

07	gallon = minivan.getNumBB (distance);

08	System.out.println (minivan.name + " requires " + gallon +

09	" gallons to travel distance " + distance + " miles.");

10	gallon = sportscar.getNumBB (distance);

11	System.out.println (sportscar.name + " requires " + gallon +

12	" gallons to travel distance " + distance + " miles.");

13

}

14

}

coding results