main() Method in Java Interview Questions and Answers for internship

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100 Java main() Method Interview Questions and Answers

  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) begins executing a program by invoking the `main()` method. Without a `main()` method with the correct signature, a Java program cannot run.

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

    • Answer: `public static void main(String[] args)`

  3. Why is `public` used in the `main()` method signature?

    • Answer: The `public` access modifier makes the `main()` method accessible from any other class, allowing the JVM to invoke it.

  4. Why is `static` used in the `main()` method signature?

    • Answer: The `static` keyword allows the `main()` method to be called without creating an instance of the class. The JVM needs to call it before any objects are created.

  5. Why is `void` used in the `main()` method signature?

    • Answer: `void` indicates that the `main()` method does not return any value.

  6. What is the purpose of `String[] args` in the `main()` method signature?

    • Answer: `String[] args` is an array of strings that allows command-line arguments to be passed to the program. Each argument entered on the command line is stored as a string in this array.

  7. 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 the entry point.

  8. Can the `main()` method be private?

    • Answer: No, because the JVM needs to access it from outside the class, and private methods are only accessible within the same class.

  9. Can the `main()` method be final?

    • Answer: Yes, but it's generally not necessary or recommended.

  10. Can the `main()` method be abstract?

    • Answer: No, because abstract methods require implementation in a subclass, but the JVM directly invokes the `main()` method.

  11. Can the `main()` method throw exceptions?

    • Answer: Yes, it can, but it's generally good practice to handle them appropriately within the `main()` method or declare them using a `throws` clause.

  12. What happens if there are multiple classes with a `main()` method in the same project?

    • Answer: You can only run one `main()` method at a time. The JVM will only execute the `main()` method of the class specified on the command line when running the program. If no class is specified, a compiler error might occur depending on the IDE/compiler.

  13. How do you access command-line arguments within the `main()` method?

    • Answer: You access them through the `args` array. For example, `args[0]` would access the first command-line argument.

  14. What happens if you don't provide any command-line arguments?

    • Answer: The `args` array will have a length of 0. You can check `args.length` to see if any arguments were provided.

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