I want to Sort a TreeSet in Java 11. I tried using a comparator, but the problem is lambda expression does not consider args as Entry.
I wanted to do this:
SortedSet<Entry<Character, Long>> sortedSet = new TreeSet<>(map.entrySet(),
((o1, o2) -> (int) (o1.getValue() - o2.getValue())));
but the problem is there's no such constructor in TreeSet. So I tried another procedure:
SortedSet<Entry<Character, Long>> sortedSet = new TreeSet<>(map.entrySet())
.comparator()
.compare(o1,o2)
compare method needed parameter:
compare(capture of ? super Entry<Character, Long> o1, capture of ? super Entry<Character, Long> o1)
but I don't know what arguments I have to pass instead of o1,o2.
Just because there is no constructor to do it all at once, doesn't mean you can't do it in 2 lines.
SortedSet<Entry<Character, Long>> sortedSet = new TreeSet<>(Comparator.comparingLong(Entry::getValue));
sortedSet.addAll(map.entrySet());
You have to create set first
SortedSet<Entry<Character, Long>> sortedSet = new TreeSet<>((o1, o2) -> (int) (o1.getValue() - o2.getValue()));
and then add elements
sortedSet.addAll(map.entrySet());
There is no way to set comparator after TreeSet
is created.
PS: Comparing values using -
is bad idea. You better use Integer.compare
or create comparator using Comparator.comparing(Entry::getValue)
.
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