Sort Map Based on Value

Map has Key and Value pair, Keys are stored in Set which removes duplicates. HashMap internally sorts the entry based on Key, So we will be using LinkedHashMap because it keeps unique elements without altering the insertion order.

package org.wesome.dsalgo;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.Set;

public class SortMap {
    public static Map<Integer, Integer> sortMap(Map<Integer, Integer> map) {
        Set<Map.Entry<Integer, Integer>> entrySet = map.entrySet();
        List<Map.Entry<Integer, Integer>> arrayList = new ArrayList(entrySet);
        Collections.sort(arrayList, (o1, o2) -> o1.getValue().compareTo(o2.getValue()));
        map.clear();
        for (Map.Entry<Integer, Integer> entry : arrayList) {
            map.put(entry.getKey(), entry.getValue());
        }
        return map;
    }
}

package org.wesome.dsalgo;

import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.Test;

import java.util.LinkedHashMap;
import java.util.Map;
import java.util.stream.IntStream;

public class SortMapTest {
    @Test
    void sortMapTest1() {
        Map<Integer, Integer> map = new LinkedHashMap<>();
        Map<Integer, Integer> testMap = new LinkedHashMap();
        int range = 5;
        IntStream.rangeClosed(0, range).forEach(i -> {
            map.put(i, range - i);
            testMap.put(range - i, i);
        });
        Assertions.assertTrue(testMap.equals(SortMap.sortMap(map)));
    }
}

plugins {
    id 'java'
}

group = 'org.wesome'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = JavaVersion.VERSION_1_8

configurations {
    compileOnly {
        extendsFrom annotationProcessor
    }
}

repositories {
    mavenCentral()
}

dependencies {
    testImplementation 'org.junit.jupiter:junit-jupiter:5.6.2'
}

test {
    useJUnitPlatform()
}