Core Java

Java Evolution
Java History
Java Features
Benefits of Java over C and C++
How Java works
The Java Programming Language
The Java Platform
Java Development Kit
HARDWARE AND SOFTWARE REQUIREMENTS
Disadvantages of Java
Overview of Java Language
Developing the Java Application
Comments in Java Code
Defining a Class
The main Method
Using Classes and Objects
Java Program Structure
Java Tokens
Constant, Variable and Datatype
Variables
Declaring Variables
Rules on Variable Names
Variable Types
Primitive Data Types
Constants
Operator and Expression
Expressions and Operators
Operator Precedence
Integer Operators
Relational Integer Operators
Floating point Operators
Relational Floating-Point Operators
String Operator
Assignment Operators
Arithmetic assignment operations
Conversions
Casts
Boolean expressions and operations
Logical operators
Bitwise operations
The complement operator
Decision making, Branching and Looping
Flow control with if and else
The if statement
The else statement
Switch statements
for, while, and do-while statements
The for statement
The while statement
The do-while statement
Using break and continue
The break statement
The continue statement
Class Object and Method
Introduction to Classes
The Benefit of Classes
Defining Classes
Class using constructor
Object
Declaring an Object
Instantiating an Object
Initializing an Object
Referencing an Object's Variables
Calling an Object's Methods
Creating a Class
The Class Declaration
The Class Body
Constructors for Classes
Implementing Methods
The Method Body
A Method's Name
Example of the Math class
The Applet Package
Array and String
Arrays
Java arrays
Object arrays
Strings
String Concatenation
Inheritance
Introduction
Creating Subclasses
Member Variables In Subclass Inherit?
Hiding Member Variables
Methods In Subclass Inherit?
Overriding Methods
Methods a Subclass Cannot Override
Methods a Subclass Must Override
The Benefits of Inheritance
Interfaces
Interfaces and Classes
Implementing and Using Interfaces
Implementing Multiple Interfaces
Creating and Extending Interfaces
Methods Inside Interfaces
Extending Interfaces
Package
Introduction
Declaring Packages
Importing Packages
Creating Our Own Packages
The Java Language Package
The Java I/O Package
The Java Utility Package
The Java Networking Package
The Applet Package
The Abstract Window Toolkit Packages
Multithreading
Introduction
Thread
Thread Attributes
Thread State
Thread Group
Methods that Operate on the Group
Access Restriction Methods
The notifyAll() and wait() Methods
Frequently used Method
Exception Handling
Introduction
What Is an Exception?
If Exceptions than?
The exception handling technique
Some Terminology
Throw an Exception
Throw, try, and catch Blocks
Multiple catch Blocks
The finally Clause
The Throwable Class
Types of Exceptions
Different List of Exception
Built-In Exceptions
Applet
Introduction
How Applets and Applications Are Different
Limitation of Applet
The Applet class
Major Applet Activities
The life cycle of a Web page applet
Including an Applet on a Web Page
Essential HTML to launch an applet and pass it parameters
Launching an applet in an HTML document
A sample applet that receives a parameter
Posting a Web page that launches a custom applet
Managing Input/Output Files in Java
Introduction
Streams
Input Streams
The Abstract Class InputStream
The File class
The FileDialog class
Low-level and high-level stream classes
The FileOutputStream class
The FileInputStream class
The DataOutputStream class
The DataInputStream class
The ObjectOutputStream class
The ObjectInputStream class

Overview of Java Language


Using Classes and Objects

The "Hello World" application is about the simplest Java program one can write that actually does something. Because it is such a simple program, it doesn't need to define any classes except for HelloWorldApp.

The "Hello World" application does use another class--the System class--that is part of the API (application programming interface) provided with the Java environment. The System class provides system-independent access to system-dependent functionality.

The bold code in the following listing illustrates the use of a class variable of the System class, and of an instance method.
 
/**
* The HelloWorldApp class implements an application that
* simply displays "Hello World!" to the standard output.
*/

class HelloWorldApp
{
public static void main(String[] args)
{
System.out.println("Hello World!"); //Display the string.
}
}
 
 
Using a Class Method or Variable
 
Let's take a look at the first segment of the statement:
System.out .println("Hello World!");  

The construct System.out is the full name of the out variable in the System class.

 
 
Using an Instance Method or Variable
 
Methods and variables that are not class methods or class variables are known as instance methods and instance variables.

While System's out variable is a class variable, it refers to an instance of the PrintStream class (a class provided with the Java development environment) that implements the standard output stream.

When the System class is loaded into the application, it instantiates PrintStream and assigns the new PrintStream object to the out class variable.

System.out.println("Hello World!");


This line of code displays "Hello World!" to the application's standard output stream