Question: Is there any way to debug only specific code or method of one of the class in an application without executing entire code from main method.
One way would be writing junit for that class and debugging it with break point.Is there any there way?

Answer: 
You can run the `HelloWorld.java` in any `package` as you want as long as there is an `entry`, which is the `public static void main(String[] args)`: 

```
public class HelloWorld {
    public static void main(String... args) {
        System.out.println("Hello world");
    }
}

```

By the way, normally we will have a `main` for each class for `unit test` as you mentioned, which provides us more power to do the job without any dependency and side effects.
There is no way to debug your class without entrypoint (junit also have entrypoint). Java entrypoint is method Main.