public SimpleCache(String id,String file,long expireTime){
  this.id=id;
  this.file=Paths.get(file);
  this.expireTime=expireTime;
}

public SimpleCache ( String id , String file , long expireTime ) { this . id = id ; this . file = Paths . get ( file ) ; this . expireTime = expireTime ; }
creates a new cache object for a single file .
