The comparator() method of java.util.TreeMap class returns the comparator used to order the keys in this map, or null if this map uses the natural ordering of its keys.
Signature
public Comparator<? super K> comparator()
This method returns the comparator used to order the keys in this map, or null if this map uses the natural ordering of its keys.
Example
The following example shows the usage of java.util.TreeMap.comparator() method.
import java.util.Comparator; import java.util.Map; import java.util.TreeMap; public class ComparatorMethodTreeMapExample { public static void main(String args[]) { // create an empty TreeMap TreeMap<Integer,String> treeMap1 = new TreeMap<Integer,String>(); // use put() method to put elements to the TreeMap treeMap1.put(1,"Element1"); treeMap1.put(2,"Element2"); treeMap1.put(4,"Element4"); treeMap1.put(5,"Element5"); //Printing the elements of the TreeMap System.out.println("**Elements of \"treeMap1\"**"); System.out.println("Size of treeMap1 is : "+treeMap1.size()); for(Map.Entry<Integer,String> entry : treeMap1.entrySet()) { System.out.println("Key : "+entry.getKey()+" Value : "+entry.getValue()); } //Using comparator() Comparator comp = treeMap1.comparator(); //Lets print the comparator following natural order System.out.println("Value of Comparator : "+comp); } }
Output
**Elements of "treeMap1"** Size of treeMap1 is : 4 Key : 1 Value : Element1 Key : 2 Value : Element2 Key : 4 Value : Element4 Key : 5 Value : Element5 Value of Comparator : null
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