code: public static void ensure(boolean condition, String message, Object... args) {
          if (!condition) {
              throw new EnsureViolation(format(message, args));
          }
      }
docs: Postcondition that supplier are supposed to ensure.
  Violations are considered to be a programming error, on the suppliers part.
  
  @param condition the assertion condition
  @param message   the fail message template
  @param args      the message template arguments
  @throws EnsureViolation if the <tt>condition</tt> is <b>false</b>