### Environment

* Dubbo version: 2.7.1
* Operating System version: Mac os
* Java version: 1.8

### Steps to reproduce this issue

1. i see the ClassUtils.getMethodName method source code,

```
public static String getMethodName(Method method, Class<?>[] parameterClasses, String rightCode) {
        if (method.getParameterTypes().length > parameterClasses.length) {
            Class<?>[] types = method.getParameterTypes();
            StringBuilder buf = new StringBuilder(rightCode);
            for (int i = parameterClasses.length; i < types.length; i++) {
                if (buf.length() > 0) {
                    buf.append(",");
                }
                Class<?> type = types[i];
                String def;
                if (type == boolean.class) {
                    def = "false";
                } else if (type == char.class) {
                    def = "\'\\0\'";
                } else if (type == byte.class
                        || type == short.class
                        || type == int.class
                        || type == long.class
                        || type == float.class
                        || type == double.class) {
                    def = "0";
                } else {
                    def = "null";
                }
                buf.append(def);
            }
        }
        return method.getName() + "(" + rightCode + ")";
    }
```
in my opinion, for(...) is to set default values for functions. But in the end, buf not used.
so, maybe should return method.getName() + "(" + buf.toString()  + ")" when for(...) end.


*
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.dubbo.common.compiler.support;
import org.apache.dubbo.common.utils.StringUtils;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.lang.reflect.Array;
import java.lang.reflect.GenericArrayType;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
/**
 * ClassUtils. (Tool, Static, ThreadSafe)
 */
public class ClassUtils {
    public static final String CLASS_EXTENSION = ".class";
    public static final String JAVA_EXTENSION = ".java";