[JAVA] Takes out the HashMap value and returns the result sorted by the value of value as a list.

Here is a summary of how to sort Map (HashMap) using value in java. Here, we are considering a situation where you want to sort the values of A_array at the same time using B_array. Since it is a form that sorts a list with an entry type of HashMap, it can be used with other Maps such as TreeMap.

code

Solution.java

import java.util.*;

class Solution {
    public static void main(String[] args) {
        int[] A_array = {1,6,3,10,5};
        int[] B_array = {8,21,13,4,5};
        tryComperator(A_array, B_array);
    }
    public static void tryComperator(int[] a, int[] b){
        Map<Integer, Integer> map = new HashMap<Integer, Integer>();
        //Store the elements of the array in hashmap.
        for (int i = 0; i < a.length; i++){
            map.put(a[i], b[i]);
        }
        //Store each element of Hashmap in a list.
        List<Map.Entry> mapValuesList = new ArrayList<Map.Entry>(map.entrySet());
        //Try to output mapValuesList.(10=It seems that it is output in the form of 4.)
        for (Map.Entry v: mapValuesList){
            System.out.println("map>> "+v+",key>> "+v.getKey()+"value>> "+v.getValue());
        }
        //Instantiate the Comparator class
        Comparator<Map.Entry> comparator = new Comparator<Map.Entry>() {
            public int compare(Map.Entry entry1, Map.Entry entry2) {
                return ((Integer) entry1.getValue()).compareTo((Integer) entry2.getValue());
            }
        };
        //Sort using comparator.
        Collections.sort(mapValuesList, comparator);
        //Output for confirmation
        for (Map.Entry s : mapValuesList) {
            System.out.println(s);
        }
    }
}

output

map>> 1=8,key>> 1value>> 8
map>> 3=13,key>> 3value>> 13
map>> 5=5,key>> 5value>> 5
map>> 6=21,key>> 6value>> 21
map>> 10=4,key>> 10value>> 4
10=4
5=5
1=8
3=13
6=21

It was output in ascending order of value.

Reference: http://kevin3sei.blog95.fc2.com/blog-entry-159.html