vdl/java: change VdlOptional<T extends VdlValue> to VdlOptional<T>

Change-Id: I5602f52af35e46775f70e36091197d1b7e098b84
diff --git a/lib/vdl/codegen/java/util_val.go b/lib/vdl/codegen/java/util_val.go
index f61f6a8..e95b815 100644
--- a/lib/vdl/codegen/java/util_val.go
+++ b/lib/vdl/codegen/java/util_val.go
@@ -136,7 +136,7 @@
 		return fmt.Sprintf("new %s(%s)", javaType(v.Type(), false, env), javaReflectType(v.TypeObject(), env))
 	case vdl.Optional:
 		if v.Elem() != nil {
-			return fmt.Sprintf("new %s(%s)", javaType(v.Type(), false, env), javaConstVal(v.Elem(), env))
+			return fmt.Sprintf("io.v.v23.vdl.VdlOptional.of(%s)", javaConstVal(v.Elem(), env))
 		} else {
 			return fmt.Sprintf("new %s(%s)", javaType(v.Type(), false, env), javaReflectType(v.Type(), env))
 		}