code: public Icon get(String url) {
          StackTraceElement[] stacks = new Exception().getStackTrace();
          try {
              Class callerClazz = Class.forName(stacks[1].getClassName());
              return get(callerClazz.getResource(url));
          } catch (ClassNotFoundException e) {
              throw new RuntimeException(e);
          }
      }
docs: Gets the icon denoted by url. If url is relative, it is relative to the
  caller.
  
  @param url
  @return an icon