src/java.base/share/classes/java/util/Formatter.java

*** 2912,2922 ****
                  break;
              case Conversion.LINE_SEPARATOR:
                  a.append(System.lineSeparator());
                  break;
              case Conversion.PERCENT_SIGN:
!                 a.append('%');
                  break;
              default:
                  assert false;
              }
          }
--- 2912,2922 ----
                  break;
              case Conversion.LINE_SEPARATOR:
                  a.append(System.lineSeparator());
                  break;
              case Conversion.PERCENT_SIGN:
!                 print("%", l);
                  break;
              default:
                  assert false;
              }
          }