Object: Objects have states and behaviors. Example: A dog has states-color, name, breed as well as behaviors -wagging, barking, eating. An object is an instance of a class.
Class: A class can be defined as a template/ blue print that describe the behaviors/states that object of its type support.
Objects in Java:
Let us now look deep into what are objects. If we consider the real-world we can find many objects around us, Cars, Dogs, Humans etc. All these objects have a state and behavior.
If we consider a dog then its state is - name, breed, color, and the behavior is - barking, wagging, running
If you compare the software object with a real world object, they have very similar characteristics.
Software objects also have a state and behavior. A software object's state is stored in fields and behavior is shown via methods.
"Object is the real word entity and blueprint of class " - G Krishna Chauhan
So in software development methods operate on the internal state of an object and the object-to-object communication is done via methods.
Classes in Java:
A class is a blue print from which individual objects are created. A sample of a class is given below:
public class xyz
{
String breed;
int age;
String color;
void a()
{
}
void b()
{
}
void c()
{
}
}
A class can contain any of the following variable types :
Local variables: variables defined inside methods, constructors or blocks are called local variables. The variable will be declared and initialized within the method and the variable will be destroyed when the method has completed.
Instance variables: Instance variables are variables within a class but outside any method. These variables are instantiated when the class is loaded. Instance variables can be accessed from inside any method, constructor or blocks of that particular class.
Class variables: Class variables are variables declared with in a class, outside any method, with the static keyword.
A class can have any number of methods to access the value of various kind of methods. In the above example, barking(), hungry() and sleeping() are methods.
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