Part 9 | Abstract Class, Exceptions, Threads | Java Programming Malayalam Tutorial

Introduction

In this tutorial, we'll explore key concepts in Java programming, specifically focusing on abstraction, exceptions, and threading. These elements are fundamental for building robust and efficient applications. By the end of this guide, you will have a deeper understanding of these concepts and how to implement them in your Java projects.

Step 1: Understanding Abstraction

Abstraction in Java allows you to focus on what an object does rather than how it does it. This is achieved through abstract classes and interfaces.

• Abstract Class:

  • Defines a blueprint for subclasses.
  • Cannot be instantiated directly.
  • Can contain both abstract methods (without a body) and concrete methods (with a body).

  Example:

  abstract class Animal {
      abstract void sound();
      void sleep() {
          System.out.println("Sleeping");
      }
  }
  

• Interface:

  • A contract that classes can implement.
  • All methods are abstract by default (Java 8 and later allows default methods).

  Example:

  interface Animal {
      void sound();
  }
  

Practical Tip

Use abstraction to hide complex implementation details and expose only the necessary parts of your objects.

Step 2: Working with Exceptions

Exceptions are events that disrupt the normal flow of a program. Java provides a robust exception handling mechanism.

• Try-Catch Block:

  • Use try to wrap code that may throw an exception.
  • Use catch to handle the exception.

  Example:

  try {
      int result = 10 / 0; // This will throw an ArithmeticException
  } catch (ArithmeticException e) {
      System.out.println("Cannot divide by zero");
  }
  

• Finally Block:

  • Executes after the try-catch block, regardless of whether an exception was thrown or not.

  Example:

  finally {
      System.out.println("This block always executes");
  }
  

Common Pitfall

Avoid using exceptions for control flow. They should be used for exceptional cases only.

Step 3: Introduction to Threads

Threads allow concurrent execution of two or more parts of a program. This can improve performance and responsiveness.

• Creating a Thread:

  • Extend the Thread class or implement the Runnable interface.

  Example using Thread:

  class MyThread extends Thread {
      public void run() {
          System.out.println("Thread is running");
      }
  }
  
  MyThread thread = new MyThread();
  thread.start();
  

  Example using Runnable:

  class MyRunnable implements Runnable {
      public void run() {
          System.out.println("Thread is running");
      }
  }
  
  Thread thread = new Thread(new MyRunnable());
  thread.start();
  

Practical Tip

Use Thread.sleep(milliseconds) to pause the execution of a thread for a specified duration.

Step 4: Synchronization in Threads

Synchronization is crucial when multiple threads access shared resources to prevent data inconsistencies.

• Use the synchronized keyword to control access to a method or block.

Example:

synchronized void display() {
    System.out.println("Synchronized method");
}

Real-World Application

Employ synchronization in scenarios where multiple threads might modify shared data, like in banking applications.

Conclusion

In this tutorial, we covered the basics of abstraction, exception handling, and threading in Java. Understanding these concepts will enhance your programming skills and enable you to build more efficient applications.

Next steps:

• Experiment with creating your own abstract classes and interfaces.
• Implement exception handling in your code to manage errors effectively.
• Try creating and managing threads to familiarize yourself with concurrent programming.