[KYLIN-4327] TOPN Comparator may violate its general contract

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: v3.1.0, v3.0.1
• Assignee: Yifei Wu
• Reporter: Yifei Wu
• Created: 06/Jan/20 03:24
• Updated: 31/Jul/20 12:11
• Resolved: 16/Jan/20 07:56

Description

in current TopN， it should save top(k) result and keep it in double value, just like this:
```
public class Counter<T> implements Serializable

{ ... protected T item; protected double count; ... }

```
But its Comparator method use "==" directly to compare the result, it may cause the error "violate its general contract" when calling it.
```
private static final Comparator ASC_COMPARATOR = new Comparator<Counter>() {
@Override
public int compare(Counter o1, Counter o2)

{ return o1.getCount() > o2.getCount() ? 1 : o1.getCount() == o2.getCount() ? 0 : -1; }

};

```

Issue Links

• links to: GitHub Pull Request #1043