Exception in thread "main" java.lang.NoSuchMethodError: main [duplicate]

This question already has answers here: Closed 10 years ago.

Possible Duplicate:

Exception in thread “main” java.lang.NoSuchMethodError: main

public class m
{
    int a; //class variable


    void f1()
    {
       int b=10;
       System.out.println(a);
       System.out.println(b);
    }
}
class B
{
   public static void main(String args[])
   {
      m ob=new m(); //object created
      ob.f1(); //calling f1 meth开发者_Go百科od

   }
}

---

I'll guess.

You are trying to invoke:

java m

Since you defined you main method in class B you should call

java B

To execute it.

Here's my test:

$cat >m.java<<. 
> public class m
> {
>     int a; //class variable
>     void f1()
>     {
>        int b=10;
>        System.out.println(a);
>        System.out.println(b);
>     }
> }
> class B
> {
>    public static void main(String args[])
>    {
>       m ob=new m(); //object created
>       ob.f1(); //calling f1 method
>    }
> }
> .
$javac m.java 
$java m 
Exception in thread "main" java.lang.NoSuchMethodError: main
$java B
0
10
$

If you see, invoking java B prints 0 10as expected.

---

Main needs to be in the top-level class whose name corresponds to the filename - so if "m" is the name of your file that's where main needs to be. Note that by convention class names start with an uppercase letter.

---

Did you invoke the Java program with java m? The main method is defined in the class B, not m, therefore, you need the java B command to invoke it. It may be confusing if you reasoned by "Same as filename.".

Also, putting two classes in one file may be a bad practice.