Session2

Memory Management

Object - oriented programming Object - oriented programming (OOP) is a fundamental style of computer programming that uses “Objects” and their interactions to design applications and computer programs. In OOPs, every real life object has properties and behaviour. This feature is achieved in java through the class and object creation. They contains properties (variables of some type) and behaviour (methods). OOPs provides better flexibility and compatibility for developing large applications.

Class :

A class defines the properties and behaviour (variables and methods) that is shared by all its objects. It is a blue print for the creation of  objects. Object : Object is the basic entity of object oriented programming language. Class itself does nothing but the real functionality is achieved through their objects. Object is an instance of the class. It takes the properties (variables) and uses the behaviour (methods) defined in the class.  Instance : One can have an instance of a class or a particular object. The instance is the actual object created at runtime. Object obj = new Object();

Encapsulation Encapsulation is the process of binding together the methods and data variables as a single entity. This keeps both the  data and functionality code safe  from the outside world. It hides the data within the class and makes it available only through  the methods.  Java provides different accessibility scopes (public , protected , private , default) to hide the data from outside.

Inheritance Inheritance allows a class (subclass) to acquire the properties and behavior of another class (superclass). In java, a class can inherit only one class(superclass) at a time but a class can have any number of subclasses. It helps to reuse, customize and enhance the existing code. So it helps to write a code accurately and reduce the development time. Java uses extends keyword to extend a class

polymorphism In object-oriented programming , polymorphism (from the Greek meaning "having multiple forms") is the characteristic of being able to assign a different meaning or usage to something in different contexts specifically, to allow an entity such as a variables, a function/method, or an object to have more than one form.  Overloading and Overriding are two types of polymorphism.

Overloaded methods are methods with the same name signature but either a different number of parameters or different types in the parameter list Overridden methods are methods that are redefined within an inherited or subclass. They have the same signature and the subclass definition is used.

Static Members

Nested Classes

System Class

Handling Strings

Wrapper Classes 

A primitive wrapper classin the Java programming language is one of eight classes provided in the java.lang package to provide object m ethods for the eight primitive types. All of the primitive wrapper classes in Java are immutable.

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Wrapper classes are used to represent primitive values when an Object is required

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Primitive type byte short int long float double Char boolean

Wrapper class Byte Short Integer Long Float Double Character Boolean

Parameters passing

Packages