Can a class which extends an abstract class be non abstract if it does not implement the methods of the abstract class it extends?

I haven't coded in Java for years now and before too didn't revise this concept properly. Recently, I read somewhere that if a class that implements a abstract class but does not implement a single method from it has to be abstract. Is it true or does it mean something else? I have not tried this out myself because currently my PC is not working and the online compiler is getting stuck on loading. So is it true? Thanks in advance.

Per the oracle docs https://docs.oracle.com/javase/tutorial/java/IandI/abstract.html#:~:text=An%20abstract%20class%20is%20a,may%20not%20include%20abstract%20methods.&text=When%20an%20abstract%20class%20is,must%20also%20be%20declared%20abstract%20.

"When an abstract class is subclassed, the subclass usually provides implementations for all of the abstract methods in its parent class. However, if it does not, then the subclass must also be declared abstract."

if we were to try to do the following:

abstract class A {
  abstract void draw();
  abstract void paint();
}

class B extends A {
  public void draw() {
    System.out.print("B implements A draw");
  }

  public void paint() {
    Systemout.print("B implements A paint");

  }
}

class C extends A {
  public void draw() {
    System.out.print("B implements A draw");
  }
}

public class Main {

  public static void main(String[] args) {
    System.out.println("Hello world!");
    B b = new B();
    C c = new C();

    b.draw();
    b.paint();
    c.draw();
    c.paint();
  }
}

Then we would get the following compiler error C is not abstract and does not override abstract method paint() in A

However, if we define C as an abstract class and then create a concrete class D that simply extends C as follows:

abstract class C extends A {
  public void draw() {
    System.out.print("C implements A draw");
  }
}

class D extends C {
   public void paint() {
      System.out.print("D implements A paint");
   }
}

and of course update our main method to where we now instantiate class D instead of C (since we cannot instantiate an abstract class) then we get a successful compile and run time. So then, as an answer, yes, if you have a class that extends an abstract class, but does not implement all of the method then it has to be abstract as well. I hope I was able to answer your question; my experience is mostly in .NET and I've grown rather stale in Java

No.

Rules are:

1. If a class contains any abstract methods (either by extending an abstract class or by having abstract methods itself), then it must be declared as abstract.
2. If a class is declared as abstract, then it is considered to be abstract regardless of the fact if it implements all abstract methods or not.

Ofcourse you can. abstract class A has not any methods,subclass B extends A and not be declared abstract.

abstract class A {
//empty
}

class B extends A {
    public void draw() {
        System.out.print("B implements A draw");
    }
}

public class Main {
    public static void main(String[] args) {
        B b = new B();
        b.draw();
    }
}