Class Fundamentals
A class is a template that defines the form of an object. It specifies both the data and the code that will operate on that data. Java uses a class specification to construct objects. Objects are instances of a class. Thus, a class is essentially a set of plans that specify how to build an object. It is important to be clear on one issue: a class is a logical abstraction. It is not until an object of that class has been created that a physical representation of that class exists in memory
The General Form of a Class
Since a class is collection of data members and member functions. Java has a plain syntax of creating class. General form of a syntax is :
class ClassName
{
access-specifier type1 variable1;
access-specifier type2 variable2;
.
.
access-specifier typeN variableN;
type method(parameters)
{
}
type method(parameters)
{
}
.
..
typeN methodN(parameters)
{
}
} // ending brace
Defining a Class
Let’s create a class for a car as:
class Car {
// data members
int gear;
int speed;
int RPM;
Car() // constructor Car called when car starts
{
RPM = 1000; // some engine RPM when car starts
}
// Member functions
void setGear(int newValue) { // set the gear to some value
gear = newValue;
}
void applyBrake(int decrement) { // break applying will decrease speed
speed -= decrement;
}
void speedUp(int increment) { // pushing accelerator will speed up car
speed += increment;
}
}
