Question

I tried this in Eclipse and it shows a compile error. However trying the same in the online IDE Compilr showed no errors. That’s why the confusion.

interface Iclass{
  void print();
  void hey();
}

class sdlfkajl implements Iclass {
  public void print(){
    System.out.println("Impl class");
  }
  public void  hey(){
    System.out.println("Hey!");
  }
  public void extra(){
    System.out.println("Should I be here?");
  }
}

The error shown is that this class cannot have methods not declared in the interface. Suggestion tooltip said I should declare this method in the interface too.

Answer 1

There is no error in your code.

You might be mistaking a warning for an error – IntelliJ can be set to flag the code above as a warning.

You might also have a setting for warnings to fail the compile.

So check your IDE settings!