How to Sort a Map in Java

Here we can get two different methods to sort a map in Java.

Source Code

1) Sort by Key

package com.beginner.examples;

import java.util.*;

public class SortMapExample1 {

	public static void main(String[] args) {

        Map map = new HashMap();
        map.put("1", "one");
        map.put("3", "three");
        map.put("2", "two");
        
        Map treeMap = new TreeMap(map);
        for (Map.Entry e : treeMap.entrySet()) {
            System.out.println("Key : " + e.getKey() + " , Value : " + e.getValue());
        }
    }
}

Output:

Key : 1 , Value : one
Key : 2 , Value : two
Key : 3 , Value : three

2) Sort by Value

package com.beginner.examples;

import java.util.*;

public class SortMapExample2 {

	public static void main(String[] args) {

        Map map = new HashMap();
        map.put("one"   , "1");
        map.put("three" , "3");
        map.put("two"   , "2");
        
        List<Map.Entry> list = new ArrayList<Map.Entry>(map.entrySet());
        Collections.sort(list,new Comparator<Map.Entry>() {
        public int compare(Map.Entry c1,
        		Map.Entry c2) {
            return c1.getValue().compareTo(c2.getValue());
        }
        });
        for(Map.Entry mapping:list){ 
        	System.out.println("Key : " + mapping.getKey() + " , Value : " + mapping.getValue()); 
        }
    }
}

Output:

Key : one , Value : 1
Key : two , Value : 2
Key : three , Value : 3

References

Imported packages in Java documentation:

• util