Java 7 Interface

interface.java

interface Logger {
    void log(String message );
}

class  InfoLogger implements Logger {
  Logger log = LoggerFactory.getLogger(InfoLogger.class);
  
  @Override
  void log( String message ) {
    log.info( message );
  }
}
 
class DebugLogger implements Logger {
  Logger log = LoggerFactory.getLogger(DebugLogger.class);
  
  @Override
  void log( String message ) {
    log.debug( message );
  }
}
 
class Logged { // logged will work with any of the above implementations
  void logHelloWorldWithSimpleLogger( Logger logger ) {
    logger.log("Hello, World");
  }
}