Only top-level class methods can be declared static

Question

I'm really hoping someone can help me here. I have tried numerous times with this code but still get the same error. I have even used other code I have found on-line that apparently 'works', but with the same error.

Below is an example of someone else's code (not mine) that they say works, but unfortunately not for me. Why is it that I am still getting the same error even with this?

public class AccountHandler {
    public static Account insertNewAccount(string AcctName)        
    {

        try{
        Account acct=new Account(Name=AcctName);
        insert acct;
        return acct;
         }
        catch (DMLException e)
        {
            System.debug('A DML exception has occurred: ' +
                         e.getMessage());
          return (NULL);
        }

    }
}

Answer 1

Credit goes to @Vamsi and if he posts I will delete (If I miss it someone please comment on this answer @me)....

An Inner class cannot have a static method. You must refactor the inner class to its own class.

This fails to compile throwing the error the OP is experiencing:

public class myExample{

    public static string doIt(Boolean optionOne){

        if(optionOne)
            return 'First';
        else
            return 'Second';

    }

    public class exampleTwo{

        public static string testIt(){
            return 'A';
        }

    }


}

However if you move the inner class exampleTwo to is own main class it will compile just fine

public class myExample{

    public static string doIt(Boolean optionOne){

        if(optionOne)
            return 'First';
        else
            return 'Second';

    }
}

Own class

    public class exampleTwo{

        public static string testIt(){
            return 'A';
        }

    }

Answer 2

In my case, all of my classes were static so when I removed the keyword static it worked.

Before public static void show_data(String start_date, String end_date) {...}

After public void show_data(String start_date, String end_date) {...}