jdk/src/java.base/share/classes/jdk/experimental/bytecode/ClassBuilder.java

*** 97,106 ****
--- 97,109 ----
          return withMethod(name, type, MB -> {
          });
      }
  
      public C withMethod(CharSequence name, T type, Consumer<? super MethodBuilder<S, T, byte[]>> methodBuilder) {
+         if (name.toString().contains(".")) {
+             throw new IllegalArgumentException("Illegal method name " + name);
+         }
          MethodBuilder<S, T, byte[]> M = new MethodBuilder<>(thisClass, name, type, poolHelper, typeHelper);
          methodBuilder.accept(M);
          M.build(methods);
          nmethods++;
          return thisBuilder();