code: public <T1 extends Throwable> 
                  RuntimeException againAs(Class<T1> t1) 
                  throws T1 {
          return againAs(t1, NULL_EX, NULL_EX, NULL_EX);
      }
docs: Throws the {@linkplain #getResolvingCause() cause} if it is the
  specified type, otherwise returns a
  {@linkplain #asRuntimeException() runtime exception}.
  <p>
  Intended to be written as {@code throw e.againAs(IOException.class)}.
  @param <T1>
  @param t1
  @return
  @throws T1