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• I have checked the FAQ of this repository and believe that this is not a duplicate.

Environment

• Dubbo version: 2.7.10
• Operating System version: macOS
• Java version: 1.8

Steps to reproduce this issue

When using method "putIfAbsent" of concurrentHashMap to produce singleton,It may create extra duplicate Object .It's better to use "computeIfAbsent" as is mentioned in java doc " The most common usage is to construct a new object serving as an initial mapped value or memoized result"