我可以使用Comparator类在Java 1.6中订购TreeMap吗？

Question

I have the following problem into a Java 6 application I try to do

QuotaTirComparator bvc = new QuotaTirComparator(mappaQuote);
TreeMap<Integer, QuotaTir> sorted_map = new TreeMap<Integer, QuotaTir>(bvc);

to obtained a sorted TreeMap.

But Eclipse give me the following error message:

The constructor TreeMap<Integer,QuotaTir>(QuotaTirComparator) is undefined

Why? Is this feature not enabled in Java 6? What is wrong? What am I missing?

Answer 1

My guess is that QuotaTirComparator is not a Comparator Obviously, the Comparator must be for the keys, not the values. As Integer already has a natural ordering, I would try removing the comparator altogether.

A Tree is sorted keys with associated values. If you want to sort the QuoteTir you need a SortedSet of them.

The Constructor which takes a comparator was adding Java 1.2 http://docs.oracle.com/javase/8/docs/api/java/util/TreeMap.html#TreeMap-java.util.Comparator-

Answer 2

Check the docs: http://docs.oracle.com/javase/6/docs/api/java/util/TreeMap.html#TreeMap(java.util.Comparator)

The comparator should compare the keys, not values.