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


Methods that Operate on the Group

The ThreadGroup class supports several attributes that are set and retrieved from the group as a whole. These attributes include the maximum priority that any thread within the group can have, whether the group is a "daemon" group, the name of the group, and the parent of the group.
The methods that get and set ThreadGroup attributes operate at the group level. That is, they inspect or change the attribute on the ThreadGroup object, but do not affect any of the threads within the group.
The following is a list of ThreadGroup methods that operate at the group level:
1. getMaxPriority(), and setMaxPriority()
2. getDaemon(), and setDaemon()
3. getName()
4. getParent(), and parentOf()
5. toString()
So for example, when we use setMaxPriority() to change a group's maximum priority, we are only changing the attribute on the group object; we are not changing the priority of any of the threads within the group.
Consider this small program that creates a group and a thread within that group:
class MaxPriorityTest
public static void main(String[] args)

ThreadGroup groupNORM = new ThreadGroup(
"A group with normal priority");
Thread priorityMAX = new Thread(groupNORM,
"A thread with maximum priority");

// set Thread's priority to max (10)

// set ThreadGroup's max priority to normal (5)

System.out.println("Group's maximum priority = " +
System.out.println("Thread's priority = " +
When the ThreadGroup groupNORM is created, it inherits its maximum priority attribute from its parent thread group.
In this case, the parent group priority is the maximum (MAX_PRIORITY) allowed by the Java runtime system.
Next the program sets the priority of the priorityMAX thread to the maximum allowed by the Java runtime system. Then the program lowers the group's maximum to the normal priority (NORM_PRIORITY).
The setMaxPriority() method does not affect the priority of the priorityMAX thread, so that at this point, the priorityMAX thread has a priority of 10 which is greater than the maximum priority of its group groupNORM. This is the output from the program:
Group's maximum priority = 5
Thread's priority = 10
As we can see a thread can have a higher priority than the maximum allowed by its group as long as the thread's priority is set before the group's maximum priority is lowered. A thread group's maximum priority is used to limit a thread's priority when the thread is first created within a group or when you use setPriority() to change the thread's priority. Note that setMaxPriority() does change the maximum priority of all of its sub-threadgroups.
Methods that Operate on All Threads within a Group
The ThreadGroup class has three methods that allow us to modify the current state of all the threads within that group:
1. resume()
2. stop()
3. suspend()
These methods apply the appropriate state change to every thread in the thread group and its subgroups.