How to force clients to provide an implementation for toString at the compiler level

gistfile1.txt

//1. create the interface with a different method than toString
interface Loggable {
  String toLogString();
}

//2. Create an abstract class that forwards toString() to this other method
abstract class LoggerBase implements Loggable {

  public String toString() {
    return toLogString();
  }

}

//3. Extend the abstract class for the children and "toLogString()" will always get called by conversions toString
public class Logger extends LoggerBase {

  public String toLogString() {
    return "Hello world!";
  }

  public static void main(String[] args) {
    Logger l = new Logger();
    System.out.println(l); //Hello world!
  }
}