TreeMap is sorted by natural order of keys, but we will implement Comparator interface to change the behaviour to sort TreeMap in descending order of keys.
import java.util.Comparator;
import java.util.Map;
import java.util.TreeMap;
/**
* @author AnkitMittal
* Copyright (c), AnkitMittal JavaMadeSoEasy.com
* Main class
*/
public class SortMapByKeyAscending {
public static void main(String...a){
Map<Integer,Integer> treeMap = new TreeMap<Integer,Integer>(new Comparator<Integer>(){
@Override
public int compare(Integer o1, Integer o2) {
//using Comparator to sort map in descending order of keys.
return o2.compareTo(o1);
}
});
treeMap.put(4, 1);
treeMap.put(2, 1);
treeMap.put(3, 1);
treeMap.put(5, 1);
System.out.println("treeMap : "+treeMap);
}
}
/*OUTPUT
treeMap : {5=1, 4=1, 3=1, 2=1}
*/
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