Question

How to sort HashMap by keys in Java

Answer 1

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

public class MyClass {
    public static void main(String args[]) {
        HashMap<String, Integer> hmp = new HashMap<String, Integer>();
 
        hmp.put("java", 4);
        hmp.put("c++", 2);
        hmp.put("c", 6);
        hmp.put("python", 5);
        hmp.put("c#", 1);
        hmp.put("php", 3);
         
        System.out.println("HashMap before sorting");
        hmp.entrySet().forEach(entry -> {
            System.out.println(entry.getKey() + " " + entry.getValue());
        });
        
        TreeMap<String, Integer> tm = new TreeMap<>(hmp);
        Set<Entry<String, Integer>> st_by_keys = tm.entrySet();
        System.out.println("HashMap after sorting by keys");
        for(Entry<String, Integer> entry : st_by_keys){
            System.out.println(entry.getKey() + " ==> " + entry.getValue());
        }
    }
}
     
     
     
     
/*
run:
     
HashMap before sorting
c# 1
c++ 2
python 5
java 4
c 6
php 3
HashMap after sorting by keys
c ==> 6
c# ==> 1
c++ ==> 2
java ==> 4
php ==> 3
python ==> 5
     
*/

 

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