code: JSField getFieldDef(int accessor, boolean mustBePresent) {
      if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) JmfTr.entry(this, tc, "getFieldDef", new Object[]{Integer.valueOf(accessor), Boolean.valueOf(mustBePresent)});
  
      if (mustBePresent) {
        if ((map == null) || (map.fields[accessor] == null)) {
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) JmfTr.exit(this, tc, "getFieldDef", null);
          return null;
        }
      }
  
      JSField result = fields[accessor];
      if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) JmfTr.exit(this, tc, "getFieldDef", result);
      return result;
    }
docs: concurrency issues.