@SuppressWarnings("unchecked")
    public static <E extends Comparable<? super E>> ComparableComparator<E> comparableComparator() {
        return INSTANCE;
    }
Gets the singleton instance of a ComparableComparator.
<p>
Developers are encouraged to use the comparator returned from this method
instead of constructing a new instance to reduce allocation and GC overhead
when multiple comparable comparators may be used in the same VM.

@param <E>  the element type
@return the singleton ComparableComparator
ttl-core/src/main/java/com/alibaba/ttl3/executor/ComparableComparator.java