In Java, does every class have to declare a main method, or is main required only in the class that serves as the application entry point?

Introduction / Context:
In Java programming, beginners are often confused about the role of the main method. Many think that every class must contain a main method, because they see examples where execution starts from public static void main(String[] args). In reality, most classes in a real world project do not have a main method at all. Only the entry point class needs it. This question checks whether you understand where main is required and how the Java Virtual Machine JVM starts a program.

Given Data / Assumptions:

• The standard entry point for a Java application is a public static void main(String[] args) method.
• A project can contain many classes, interfaces, enums, and other types.
• The JVM is instructed to start execution from a specific class that has an appropriate main method.
• Supporting classes are instantiated or referenced from that entry point or from other classes, without needing their own main method.

Concept / Approach:
The main method is a static method with a specific signature. When you run java SomeClass on the command line, the JVM looks inside SomeClass for a main method with the correct signature and begins executing statements inside it. All other classes in the application can define any methods and fields that make sense for the design, and the compiler does not insist on a main method in those classes. Libraries and frameworks often consist entirely of classes that have no main method at all, because they are meant to be used by other applications rather than launched directly.

Step-by-Step Solution:
Step 1: Recall that the compiler only requires classes to obey Java syntax rules; it does not require every class to define main. Step 2: Understand that the JVM needs exactly one entry point per launched application, which is a public static void main(String[] args) method. Step 3: Recognise that you can have multiple classes with main in a project, but you choose which one to run by specifying the class name when launching the application. Step 4: Note that utility, model, and helper classes are typically created without any main method and are used via references from the entry point or framework code. Step 5: Conclude that main is compulsory only in at least one class that you intend to run as a standalone Java application, not in every class.

Verification / Alternative check:
You can verify this by writing a simple project with two classes. Let ClassA contain the main method and ClassB contain only a normal instance method. Compile and run ClassA. The program will work correctly even though ClassB has no main method. If you try to run ClassB directly with the java command, the JVM will complain that it cannot find the main method, which shows that main is needed only when you try to start execution from that specific class.

Why Other Options Are Wrong:
Option b claims that every class must declare main for compilation. This is false because library classes compile and run perfectly without it. Option c mentions abstract classes, which is unrelated to the requirement for main. Option d incorrectly states that main belongs in interfaces, but interfaces cannot contain traditional static main methods in older Java versions, and even in newer versions the entry point is still normally a class, not an interface.

Common Pitfalls:
A common mistake is to treat main as a magic method that every class needs. Another is to confuse the concept of an entry point with general class design. Keep in mind that main is only the starting location for program execution, while most classes are simply used as building blocks for the application logic.

Final Answer:
The correct statement is that the main method is required only in the class that serves as the entry point of the application; other supporting classes do not need a main method.