Bad way of doing double check

BrokenDoubleCheck.java

class BrokenDontUse {
  private Map<String, SomeResource> aHashMap = new HashMap<>();

  public SomeResource getResource(String name) {
    SomeResource r = aHashMap.get(name);
    if(r != null) {
      return r;
    }
    synchronized(aHashMap) {
      SomeResource r = aHashMap.get(name);
      if(r != null) {
        return r;
      }
      r = new SomeResource(name);
      aHashMap.put(name, r)
      return r;
    }
  }
}