Java Program with Local Class in Method - Car and Engine

Java Nested Classes: Exercise-3 with Solution

Local Class:
Write a Java program to create a class called Car with a method startEngine(). Inside this method, define a local class Engine that has a method run(). The run() method should print "Engine is running". Instantiate and call the run() method from within the startEngine() method.

Sample Solution:

Java Code:

Car.java

// Class Car
public class Car {
    
    // Method startEngine
    public void startEngine() {
        // Local class Engine inside startEngine method
        class Engine {
            // Method run in local class Engine
            public void run() {
                // Print statement indicating the engine is running
                System.out.println("Engine is running");
            }
        }
        
        // Creating an instance of the local class Engine
        Engine engine = new Engine();
        // Calling the run method of the local class Engine
        engine.run();
    }
    
    // Main method to demonstrate the local class
    public static void main(String[] args) {
        // Creating an instance of Car
        Car myCar = new Car();
        // Calling the startEngine method
        myCar.startEngine();
    }
}

Output:

Engine is running

Explanation:

• Class Car: The outer class that contains the method startEngine().
• Method startEngine(): This method contains the local class Engine.
• Local class Engine: Defined within the startEngine() method and has a method run().
• Method run(): Prints "Engine is running".
• Instantiate Engine: Inside startEngine(), an instance of the local class Engine is created and the run() method is called.
• Main method: Demonstrates the usage of the local class by creating an instance of Car and calling the startEngine() method.

Note on Java Nested Classes:

Java nested classes allow for different levels of nested class usage. Local classes are defined within a block, typically a method, and can only be accessed within that block. In this exercise, the Engine class is a local class within the startEngine() method of the Car class, allowing it to encapsulate the logic for starting the engine within that method. This enhances code organization and encapsulation.

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