code: public void ifExceptionThrowRuntime() throws Error {
          if(nested == null || nested.isEmpty()) {
              return;
          }
          if (nested.size() == 1) {
              Throwable th = nested.get(0);
              if (th instanceof Error) {
                  throw (Error)th;
              } else if (th instanceof RuntimeException) {
                  throw (RuntimeException)th;
              } else {
                  throw new RuntimeException(th);
              }
          }
          throw new RuntimeException(this);
      }
docs: Throw a Runtime exception.
  If this multi exception is empty then no action is taken. If it
  contains a single error or runtime exception that is thrown, otherwise the this
  multi exception is thrown, wrapped in a runtime exception.
  
  @exception Error if this exception contains exactly 1 {@link Error}
  @exception RuntimeException if this exception contains 1 {@link Throwable} but
  it is not an error, or it contains more than 1 {@link Throwable} of any type