Why does the main function in Java reside in a class?

how to call main method in java
main class in java
why main method is static in java javatpoint
why main method is public in java
purpose of main method in java
how to call a class from main class in java
methods are always part of a class.
java main class command line

I just started studying Java. And the main function of the program always resides in a class.

public class t{
  public static void main(String[] args){
  // do stuff
  }
}

I have studied C++, and in there the main function doesn't need to be in a class. Why in Java we have to do that?

Why can't the main function exist in Java without a class, like it does in C++?

Probably for the same reason you put question marks at the end of a question: that's just how they decided it's done.

The main method is the result of a convention that says "this is how the entry point's method signature should look" which doesn't exempt it from language semantics.

Java does not support methods outside of classes/interfaces and as such it has to be contained in one.

A Main Class in Java Contains the Main Method, Thanks to Ask, Main Method is very important to start our code Execution , when we start writing code then we have Devbrat Shukla(देवब् त शु क्ला), lived in Pune, Maharashtra, India Can I run a program in Java without main class? According to Java standards and common practices, we should declare every class in its own source file. And even if we declare multiple classes in a single source file (.java), still each class

Because that is how the language was designed. The JVM first loads the class containing the main function and then calls the main() method. Without loading the class, main() cannot be called, i.e, main() doesn't exist without its enclosing class.

Why is the main method in Java important?, Instance method are methods which require an object of its class to be created before it can be called. They can be called within the same class in which they reside or from the different classes public static void main (String[] args) {. The particular form of main is required by Java. While the following explanation of its parts is not needed now, and probably not especially understandable, you can return to it later when you know more. In Java, main is a static method. This means the method is part of its class and not part of objects. Robots are objects.

  1. All methods must reside in a class in Java.
  2. main is a method.

Therefore, main must reside in a class.

Furthermore, a class is not just a blueprint of an object. It is by itself a chunk of code that does something. One of the things it does is providing the entry point of the application by containing a main method.

Static methods vs Instance methods in Java, JVM launches the java program by invoking the main() method. Static is a keyword. The role of adding static before any entity is to make that entity a class entity. main() is a function just like any other C function, so the location of the two parameters argc and argv will follow standard for the compiler on the platform. e.g. for most C compilers targeting x86 they will be on the stack just above the return address and the saved base pointer (the stack grows downwards, remember).

Because everything is inside a class in Java. Java code consists only of classes. They may be nested in themselves or in a packagehierarchy, but nothing is allowed to appear outside of a class.

The only exceptions are the package and import statements.

Understanding "static" in "public static void main" in Java , Selection from Head First Java, 2nd Edition [Book] The Dog class has an instance variable size, that the bark() method uses to decide what kind of bark sound  @rents No, the bytecode is stored in .class files (in JARs). The original source code (in the .java) files is gone. In this way Java is like C (only it compiles to a well-defined IL and not a specific machine target). – user2864740 Oct 2 '14 at 5:29

The "every method in Java must be in a class because the spec says so" answer is only part of the story. By having main() inside a class it is possible to have multiple entry points within a project. i.e. multiple classes with main() methods. This allows you to select a different main class at runtime rather than compile time. e.g.

java -cp program.jar com.example.Class1

or then if you want to run a different main from the same jar

java -cp program.jar com.example.Class2

4. Methods Use Instance Variables: How Objects Behave, In the examples in this specification, this first class is typically called Test . will typically start a Java Virtual Machine by invoking method main of class Test that can be accessed in any potential continuing computation from any live thread. The public class name should be the name of the source file as well which should be appended by .java at the end. For example: the class name is public class Employee{} then the source file should be as Employee.java. If the class is defined inside a package, then the package statement should be the first statement in the source file.

Chapter 12. Execution, Objects are basic building blocks of a program. Basic characteristics of methods are: The following are typical names of methods in Java: class Base { public void showInfo() { System.out.println("This is Base class"); } } same name, but they are not in conflict because they reside in different scopes. Creating an object of a class is like constructing a building by referring to its blue print. Here Building is the Object and Blue Print is analogous to a Class. I hope it simplifies your concept of Object instantiation from a Class.

Methods in Java - parameters, hiding, overriding, Java Multiple Methods In One Class : This program shows how we can create multiple methods in a class and how we can public static void main(String arg​[]) A python module is nothing but a package to encapsulate reusable code. Modules usually, but not always, reside in a folder with a __init__.py file inside of it. Modules can contain functions but also classes. Modules are imported using the import keyword.

Java Multiple Methods In One Class Example Program, I created new project, new class (Main.java) and must write " public static void main(String[] args){} " It will be good if Standard Library Methods. The standard library methods are built-in methods in Java that are readily available for use. These standard libraries come along with the Java Class Library (JCL) in a Java archive (*.jar) file with JVM and JRE.

Comments
  • @haim770 Not really, primitive types are still here.
  • @haim770 That was not the answer I was looking for. I meant, that by definition a class is a template of a real world object right? So, WHY DOES JAVA NEED A CLASS? WHY CANT THE MAIN FUNCTION EXIST WITHOUT A CLASS?
  • So, there wasn't any specific reason for including the main function in the class? They could have just allowed a main function without a class and it would have made no difference?
  • @ooodddbbb - It makes a lot of difference. The language was designed that way. Only when a class is loaded, we will ahve access to its members. So to access main() we need to load the enclosing class.
  • @TheLostMind That made a lot of sense. Also, main is the only member of that class which contains it right? Thanks Anyways
  • @ooodddbbb - No. Like this answer clearly states, The main method is the result of a convention that says "this is how the entry point's method signature should look" which doesn't exempt it from language semantics.. C++ is not Java, the signatures and behavior are different.
  • @ooodddbbb It makes an immeasurable difference. The whole of Java platform is based on the premise of a class as a code module. Classes are what you load to get executable code. They are the .so libraries of Javaspace. Get over it---the sooner the better.