Salient Features of Java - 1

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Presented ByJanani JayarajYamini Udayakumar

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Contents

Java-Features OOPS Concepts:

Encapsulation

Inheritance

Multithreading

Thread-Life Cycle

Synchronization

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Features Of Java

• Platform Independence (Write Once run any where)

• Object Oriented (No coding outside class )

• Compiler/Interpreter Combo (Extensive code checking)

• Robust (easy )

• Several dangerous features of C & C++ eliminated

• Automatic Memory Management (memory management by JVM)

• Security

• Dynamic Binding (linking of data & methods at runtime)

• Good Performance (just in-time Compilation)

• Threading (Multiprocessing)

• Built-in Networking(Internet Communications)

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Encapsulation

• Encapsulation is the process of hiding all the details of an entity that do not contribute to its essential characteristics

For example,

a procedure is a type of encapsulation because it combines a series of computer instructions.

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ENCAPSULATION

• Encapsulation hides the implementation of an abstraction from its users

• Encapsulation is often reffered to as Information hiding

• Only the interface to an abstraction should be known to its clients

• How that interface is implemented is hidden for the client

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The only way to access the state of the object should be via the methods provided in its interface

The methods encapsulates the states

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• Inheritance is the creation of one class(sub class) by extending another class(super class) so that instances of the new class automatically inherit the fields and methods of its parent class.

• Example

Inheritance

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class Account {Account(){System.out.println("Parent Class");} }Class Savings extends Account{Savings(){System.out.println("In Saving Child Class");} }Class Current extends Account{Current(){System.out.println("In Current Child Class");}}

public static void main(String arg[]){Account child=new Saving();Account child1=new Current();}}

Super class

Sub classes

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Types Of Inheritance

Single Level Inheritance(only one super class) Multilevel Inheritance(derived from derived class) Hierarchical Inheritance(one super class many sub class) Multiple Inheritance(several super classes Hybrid Inheritance(more than two types)

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Multi Threading

• Execution program with multiple threads in parallel

• Special form of multiprocessing

• Creating threads in java

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New Ready to run Running Dead

blocked/waiting/sleeping

start() run() destroy()

notify()/notifyAll() Sleep()/wait()/blocked()

Thread created

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Thread ready to run

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Thread is running

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notify()/notifyAll() sleep()/wait()/blocked()

Thread in blocked , waiting, sleep state

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Thread terminated

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Thread States

New:

It is when the thread object is created Runnable State:

• When start() method is called on a thread it goes into a ready to run state i.e. Runnable

• When interrupt() method is used on a running thread, it comes into a ready state

• There can be many threads in a runnable state.

• A thread can again come to runnable state after running or coming back

from sleeping, waiting or blocked state.

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Thread States (Cont…)

Sleeping state:

• Sleep() is a static method and executed on currently executing thread

• It is used to delay execution for a period of time.CPU is not used by that thread for that mentioned period of time

• Even if a thread goes to sleep, it doesn’t release the locks Blocked State:

• If a thread is waiting for an indefinite time until I/o takes place, then a then the thread is said to be in blocked state

Dead:

• When a thread completes its run() method it is said to be dead

• A dead thread is always dead

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Thread CreationThread can be created in 2 ways:

• Extending Thread class and overriding the public void run() method

• Implementing Runnable Interface and adding the code to be executed by the thread in void run() method.

A runnable object is created & it is passed as an arguments to the thread class constructor to create the Thread

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Creating Threads

• Runnable Interface:• Create Object Implementing Runnable Interface

• Pass it to thread object via Thread constructor

Example• Public class T implements Runnable {

• Public void run()

• { //working of thread}}

public class Thread{

Public static void main(String args[]);

{

Thread thread=new Thread(new NewThread());

Thread. start();

}}

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Creating Threads(Cont…)

• Extends Thread Class

public class T extends thread{

public void run(){//Working of thread}

}

T t=new T();

t.start();

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Synchronization

1. Two or more threads accessing the same data simultaneously may lead to loss of data integrity.

2. In order to avoid this java uses the concept of monitor. A monitor is an object used as a mutually exclusive lock.

3. At a time only one thread can access the Monitor. A second thread cannot enter the monitor until the first comes out. Till such time the other thread is said to be waiting .

4. The keyword Synchronized is use in the code to enable synchronization and it can be used along with a method.

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InterProcess Communication

• wait() tells the calling thread to give up the monitor and go to sleep until some other thread enters the same monitor and calls notify().

• notify() wakes up a thread that called wait() on the same object.

• notifyAll() wakes up all the threads that called wait() on the same object. One of the threads will be granted access.

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Thank You

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Single Inheritance

• Single Inheritance – Derived class has only one direct base class – Creates “simple” hierarchy of classes - trees – One to one inheritance of members – Specializes a base class

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Single Inheritance

• Single Inheritance

– Derived class has only one direct base class

– Creates “simple” hierarchy of classes - trees

– One to one inheritance of members

– Specializes a base class

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Multilevel Inheritance

Subclass is derived from a derived class then this mechanism is known as the multilevel inheritance.Eg: Grandfather, son, Grandson

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Multilevel Inheritance

Super class

Intermediate class

Sub class

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Hierarchical Inheritance

It is that having one super class and many sub classesCertain features of one level can be shared by other levelsEg:Saving account & current account acquires the properties of Account class

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Multiple & Hybrid Inheritance

• Multiple Inheritance:

Java does not support Multiple Inheritance

To achieve this ,we use the concept of Interface

• Hybrid Inheritance:

Java does not support Hybrid Inheritance since it is a composition of Multilevel & Multiple Inheritance

Salient Features of Java - 1

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