- [ ] I have searched the [issues](https://github.com/apache/dubbo/issues) of this repository and believe that this is not a duplicate.
- [ ] I have checked the [FAQ](https://github.com/apache/dubbo/blob/master/FAQ.md) of this repository and believe that this is not a duplicate.

### Environment

* Dubbo version: xxx
* Operating System version: xxx
* Java version: xxx

### Steps to reproduce this issue

![image](https://user-images.githubusercontent.com/8758457/59562427-2e06c800-905f-11e9-9bff-9ea54d87fc6d.png)
![image](https://user-images.githubusercontent.com/8758457/59562435-51317780-905f-11e9-930b-a66bc866ccf1.png)


Pls. provide [GitHub address] to reproduce this issue.

### Expected Result

What do you expected from the above steps？

### Actual Result

What actually happens?

If there is an exception, please attach the exception trace:

```
Just put your stack trace here!
```

public void setLastAccessTime(long lastAccessTime) {
            this.lastAccessTime.set(lastAccessTime);
        }
        public K getKey() {
            return key;
        }
        public V getValue() {
            return value;
        }
        @Override
        public boolean equals(Object obj) {
            return value.equals(obj);
        }
        @Override
        public int hashCode() {
            return value.hashCode();
        }
        @Override
        public String toString() {
            return "ExpiryObject{" +
                    "key=" + key +
                    ", value=" + value +
                    ", lastAccessTime=" + lastAccessTime +
                    '}';
        }
    }
    /**
     * Background thread, periodically checking if the data is out of date
     */
    public class ExpireThread implements Runnable {