OOP CONCEPTS

POLYMORPHISM

• Ability to identify a function to run.
• One name many forms.(some object/function behaving as many forms)

1)Compile time(Overloading)

• Also called method and operator overloading.
• Method with same name,but different signature,signature means:

1.  No. of parameters
2. Type of parameters
3. Order of parameters

2)Run-time(Overriding)

• Method of base class is re-defined in the derived class.
• Method with same name,same signature and exactly the same return type.

INHERITANCE

• Child class allows to inherit properties from its parent class(extends keyword).
• Access only public/protected.

Multiple inheritance

• Child class inherit properties from multiple classes.
• Java does not allow extend multiple classes.
• Problem with multiple inheritance: 

If multiple parents have methods with same name,then at run at run time difficult to decide for the compiler,which method to execute.

• To overcome this problem,Java allows to implement multiple interfaces.

ABSTRACTION

• Converting real world objects in term of class.
• Concept of defining an idea in term of classes or interfaces.

ex:-

public class Vehicle{

     public string model;

}


ENCAPSULATION

• Considered as Hiding data
• Combining methods & attributes into a class
• Users access private attributes via public methods

ex:-

public class Person{

     private string name;

     public void setName(){
        this.name= "Lahiru";
     }

     public string getName(){
        return name;
     }

}