Program to convert HashMap to TreeMap in Java

At first create a HashMap −

Map<String, String> map = new HashMap<>();
map.put("1", "One");
map.put("2", "Two");
map.put("3", "Three");
map.put("4", "Four");
map.put("5", "Five");
map.put("6", "Six");

Now, convert the above HashMap to TreeMap −

Map<String, String> treeMap = new TreeMap<>();
treeMap.putAll(map);

Example

Following is the program to convert HashMap to TreeMap in Java −

import java.util.*;
import java.util.stream.*;
public class Demo {
   public static void main(String args[]) {
      Map<String, String> map = new HashMap<>();
      map.put("1", "One");
      map.put("2", "Two");
      map.put("3", "Three");
      map.put("4", "Four");
      map.put("5", "Five");
      map.put("6", "Six");
      map.put("7", "Seven");
      map.put("8", "Eight");
      map.put("9", "Nine");
      System.out.println("HashMap = " + map);
      Map<String, String> treeMap = new TreeMap<>();
      treeMap.putAll(map);
      System.out.println("TreeMap (HashMap to TreeMap) " + treeMap);
   }
}

Output

HashMap = {1=One, 2=Two, 3=Three, 4=Four, 5=Five, 6=Six, 7=Seven, 8=Eight, 9=Nine}
TreeMap (HashMap to TreeMap) {1=One, 2=Two, 3=Three, 4=Four, 5=Five, 6=Six, 7=Seven, 8=Eight, 9=Nine}