main() Method in Java Interview Questions and Answers for 2 years experience

1. What is the main() method in Java?

   • Answer: The main() method is the entry point of execution for a Java program. The Java Virtual Machine (JVM) starts executing a program by invoking the main() method. Without a correctly defined main() method, a Java program cannot run.

2. What is the signature of the main() method?

   • Answer: The standard signature is: public static void main(String[] args). public means it's accessible from anywhere. static means it belongs to the class, not a specific object. void indicates it doesn't return a value. String[] args is an array of strings that can hold command-line arguments passed to the program.

3. Can the main() method be overloaded?

   • Answer: No, the JVM specifically looks for the public static void main(String[] args) signature. While you can have other methods named main, only this specific signature will be executed as the entry point.

4. Can the main() method be private?

   • Answer: No. The JVM needs to access the main() method, and a private method is not accessible from outside the class.

5. Can the main() method be final?

   • Answer: Yes, it can be declared final, preventing it from being overridden in subclasses. However, this is rarely done.

6. What happens if the main() method is not declared as public?

   • Answer: The program will not compile. The JVM requires the main() method to be public to access it.

7. What happens if the main() method is not declared as static?

   • Answer: The program will not compile. A non-static method requires an object instance to be called, but the JVM needs to call main() before any objects are created.

8. What happens if the main() method is not declared as void?

   • Answer: While not standard, it's technically possible to have a main method that returns a value (e.g., int main(String[] args)). However, the return value will be ignored by the JVM.

9. What is the purpose of the String[] args parameter in the main() method?

   • Answer: The String[] args parameter allows you to pass command-line arguments to your Java program. Each command-line argument is stored as a string in the array.

10. How do you access command-line arguments in the main() method?

    • Answer: You can access them using the array index (e.g., args[0] accesses the first argument, args[1] the second, and so on). args.length gives the number of arguments.

11. What are some best practices for writing the main method?

    • Answer: Keep it concise, focusing on program initialization and calling other methods to handle core functionality. Use meaningful variable names. Handle potential exceptions gracefully. If the program takes command line arguments, include clear instructions on how to use them.

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