Synchronized on `String#intern` is a bad practice, interning a string will make it a global object .Which means if you synchronized the same interned strings in different parts of your code , some shit'll happen ,eg : deadlock

https://github.com/alibaba/dubbo/blob/9cf27a36848c22fbfd00877449fbe0eaf53e040c/dubbo-rpc/dubbo-rpc-default/src/main/java/com/alibaba/dubbo/rpc/protocol/dubbo/DubboProtocol.java#L333
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 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
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 *
 *     http://www.apache.org/licenses/LICENSE-2.0
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package com.alibaba.dubbo.rpc.protocol.dubbo;
import com.alibaba.dubbo.common.Constants;
import com.alibaba.dubbo.common.URL;
import com.alibaba.dubbo.common.extension.ExtensionLoader;
import com.alibaba.dubbo.common.serialize.support.SerializableClassRegistry;
import com.alibaba.dubbo.common.serialize.support.SerializationOptimizer;
import com.alibaba.dubbo.common.utils.ConcurrentHashSet;
import com.alibaba.dubbo.common.utils.ConfigUtils;
import com.alibaba.dubbo.common.utils.NetUtils;