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
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
Declaring Variables
Rules on Variable Names
Variable Types
Primitive Data Types
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
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
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
Java arrays
Object arrays
String Concatenation
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 and Classes
Implementing and Using Interfaces
Implementing Multiple Interfaces
Creating and Extending Interfaces
Methods Inside Interfaces
Extending Interfaces
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
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
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
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
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
Examples of Core Java
A simple program printing 'Hello'.
Writing the first ten multiples of any number using for loop.
To check whether a number is a PERFECT NUMBER or not.
A simple program using accumulator.
Calculate the square of the numbers from 1 to 10


Thread Group

All threads belong to a thread group. ThreadGroup, a java.lang class, defines and implements the capabilities of a group of related threads.
The ThreadGroup class manages groups of threads for Java applications. A ThreadGroup can contain any number of threads. The threads in a group are generally related in some way, such as who created them, what function they perform, or when they should be started and stopped.
ThreadGroups can contain not only threads but also other ThreadGroups. The top most thread group in a Java application is the thread group named "main". We can create threads and thread groups in the "main" group. We can also create threads and thread groups in subgroups of "main" and so on.
The result is a root-like hierarchy of threads and thread groups.


The ThreadGroup class has methods that can be categorized as follows:
1. Collection management Method:-methods that manage the collection of threads and     subgroups contained in the thread group.
2. Method that Operate on the Group:-these methods set or get attributes of the      ThreadGroup object.
3. Method that Operate on All Threads within a Group --this is a set of methods that     perform some operation, such as start or resume, on all the threads and subgroups     within the ThreadGroup.
4. Access Restriction Methods:-ThreadGroup and Thread allow the security manager to     restrict access to threads based on group membership.
Collection Management Methods
The ThreadGroup provides a set of methods that manage the threads and subgroups within the group and allow other objects to query the ThreadGroup for information about its contents.
For example,
You can call ThreadGroup's activeCount() method to find out the number of active threads currently in the group. The activeCount() method is often used with the enumerate() method to get an array filled with references to all the active threads in a ThreadGroup.
For example,
The listCurrentThreads() method in the following example fills an array with all of the active threads in the current thread group and prints their names:
class EnumerateTest
void listCurrentThreads()
ThreadGroup currentGroup = Thread.currentThread().getThreadGroup();
int numThreads;
Thread[] listOfThreads;

numThreads = currentGroup.activeCount();
listOfThreads = new Thread[numThreads];
for (int i = 0; i < numThreads; i++) {
System.out.println("Thread #" + i + " = " + listOfThreads[i].getName());
Other collection management methods provided by the ThreadGroup class include activeGroupCount() and list().