Using parameterized advice to count how many times a track is played

TrackCounter.java

package soundsystem;

import java.util.HashMap;
import java.util.Map;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.Pointcut;

@Aspect
public class TrackCounter{
  private Map<Integer, Integer> trackCounts = new HashMap<Integer, Integer>();
  
  /**
   * The thing to focus on is the args(trackNumber) qualifier in the pointcut expression.
   * This indicates that any int argument that is passed into the execution of playTrack()
   * should also be passed into the advice. The parametername, trackNumber, also matches 
   * the parameter in the pointcut method signature.
   */ 
  @Pointcut("execution(* soundsystem.CompactDisc.playTrack(int)) and args(trackNumber)")
  public void trackPlayed(int trackNumber){}
  
  @Before("trackPlayed(trackNumber")
  public void countTrack(int trackNumber){
    int currentCount = getPlayCount(trackNumber);
    trackCounts.put(trackNumber, currentCount + 1);
  }
  
  public int getPlayCount(int trackNumber){
    return trackCounts.containsKey(trackNumber) ? trackCounts.get(trackNumber) : 0;
  }
}