java not detecting main function

[covert harbor]

class Parent {
  int a = 10;
}
class Child extends Parent {
  int b = 10;
  public static void main(String[] args) {
    Child c = new Child();
    System.out.println(c.a * c.b);
  }
}

why this doesn't work and

[supple parrot]

Detected code, here are some useful tools:

Formatted code

class Parent {
  int a = 10;
}
class Child extends Parent {
  int b = 10;
  public static void main(String[] args) {
    Child c = new Child();
    System.out.println(c.a * c.b);
  }
}

<@&987246399047479336> please have a look, thanks.

[supple parrot]

While you are waiting for getting help, here are some tips to improve your experience:

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[covert harbor]

class Child extends Parent {
  int b = 10;
  public static void main(String[] args) {
    Child c = new Child();
    System.out.println(c.a * c.b);
  }
}
class Parent {
  int a = 10;
}

this work

[supple parrot]

Detected code, here are some useful tools:

Formatted code

class Child extends Parent {
  int b = 10;
  public static void main(String[] args) {
    Child c = new Child();
    System.out.println(c.a * c.b);
  }
}
class Parent {
  int a = 10;
}

[ornate hamlet]

it does work. ur likely just running it incorrectly

show how u execute it please

and then also share the errors u get

[wraith chasm]

@covert harbor

[wraith chasm]

make the class with the main method public and name the file after the public class

[wraith chasm]

huh, maybe move Parent under the Child class

[covert harbor]

see this is working correctly that's why i asked

does java requires class with main function on top

java version for reference

[wraith chasm]

I dont think though

[wraith chasm]

but not sure

but you shouldnt really have multiple top level classes in one file anyways

[covert harbor]

yeah i'm learning in college

they have this example

[wraith chasm]

just one public class with same name as the file

[covert harbor]

yeah but this should work right?

[wraith chasm]

not sure how this example was given but they might mean that they are in different files

let me test it

[covert harbor]

see there is two different class but this is working

[wraith chasm]

works fine like this

even without public class it works

[covert harbor]

other way parent should be on top

[wraith chasm]

then its not working

seems like class with main method needs to be on top

wasnt aware

[covert harbor]

yeah that's why i'm thinking is there any reference or rule where it says that

[wraith chasm]

probably in the jls (java language specification)

https://docs.oracle.com/javase/specs/jls/se20/jls20.pdf

800+ pages

[ornate hamlet]

its bc of the shorthand syntax java Foo.java

divide it into the full commands and it works

javac Foo.java

java Child

note how javac takes the name of the file, not classes

and java then takes the name of the class

the shorthand syntax was introduced for small one class programs only, as convenience

it doesnt work on more complex setups

i dont think this particular part is explained in the jls, but in the javac specification instead

since that has nothing to do with the language itself, but rather how they decided to design their program apis

[covert harbor]

yeah this is working thanks

[deep plaza]

yeah it does