java使用hashMap缓存保存数据的方法

private static final hashmap<long, xxx> scache = new hashmap<long, xxx>();
private static int sid = -1;
public static void initalbumartcache() {
  try {
    //。。。
    if (id != sid) {
      clearcache();
      sid = id; 
    }
  } catch (remoteexception e) {
    e.printstacktrace();
  }
}
public static void clearcache() {
  synchronized(scache) {
    scache.clear();
  }
}
public static xxx getcachedxxx(long index, bitmapdrawable defaultbitmap) {
  xxx d = null;
  synchronized(scache) {
    d = scache.get(index);
  }
  if (d == null) {
    //。。。
    synchronized(sartcache) {
      // the cache may have changed since we checked
      xxx value = scache.get(index);
      if (value == null) {
        scache.put(index, d);
      } else {
        d = value;
      }
    }
  }
  return d;
}