How to sort Map values by key in Java?

Question

I have a Map that has strings for both keys and values.

Data is like following:

\"question1\", \"1\"
\"question9\", \"1\"
\"que

Answer 1

If you already have a map and would like to sort it on keys, simply use :

Map treeMap = new TreeMap(yourMap);

A complete working example :

import java.util.HashMap;
import java.util.Set;
import java.util.Map;
import java.util.TreeMap;
import java.util.Iterator;

class SortOnKey {

public static void main(String[] args) {
   HashMap hm = new HashMap();
   hm.put("3","three");
   hm.put("1","one");
   hm.put("4","four");
   hm.put("2","two");
   printMap(hm);
   Map treeMap = new TreeMap(hm);
   printMap(treeMap);
}//main

public static void printMap(Map map) {
    Set s = map.entrySet();
    Iterator it = s.iterator();
    while ( it.hasNext() ) {
       Map.Entry entry = (Map.Entry) it.next();
       String key = (String) entry.getKey();
       String value = (String) entry.getValue();
       System.out.println(key + " => " + value);
    }//while
    System.out.println("========================");
}//printMap

}//class