Fix for issue 20796

pkg/analyzer/lib/src/generated/java_core.dart

 library java.core;
 
 final Stopwatch nanoTimeStopwatch = new Stopwatch();
 
 const int LONG_MAX_VALUE = 0x7fffffffffffffff;
 
 class JavaSystem {
   static int currentTimeMillis() {
     return (new DateTime.now()).millisecondsSinceEpoch;
   }
@@ skipping 136 matching lines @@
         markFound = false;
       } else {
         markFound = true;
       }
       continue;
     }
     if (markFound) {
       markFound = false;
       // %d
       if (c == 0x64) {
-        sb.writeCharCode(args[argIndex++]);
+        sb.write(args[argIndex++]);
         continue;
       }
       // %s
       if (c == 0x73) {
-        sb.writeCharCode(args[argIndex++]);
+        sb.write(args[argIndex++]);
         continue;
       }
       // unknown
       throw new IllegalArgumentException('[$fmt][$i] = 0x${c.toRadixString(16)}');
     } else {
       sb.writeCharCode(c);
     }
   }
   return sb.toString();
 }
@@ skipping 248 matching lines @@
  *     format('{0} are you {1}ing?', ['What', 'read']) = 'What are you reading?'
  */
 String formatList(String pattern, List args) {
   return pattern.replaceAllMapped(new RegExp(r'\{(\d+)\}'), (match) {
     String indexStr = match.group(1);
     int index = int.parse(indexStr);
     var arg = args[index];
     return arg != null ? arg.toString() : null;
   });
 }