How can we find the name of the employee having second highest salary in a Map(key -employee name, value-salary) using java 8 stream API?

We have a map Map<String, Long> which store employee name as string and employee salary as value. The task is to get the name with of the employee who has the second highest salary among the employees stores in this hashmap.

Consider the following map as input

Map<String,Integer> map = new HashMap<>();
    map.put("anil",1000);
    map.put("ankit",1200);
    map.put("bhavna",1300);
    map.put("james",1400);
    map.put("micael",1500);
    map.put("tom",1600);
    map.put("daniel",1700);

We want to fetch second highest salary with employee name. This can be achieved by below code.

Map.Entry<String,Integer> finalResult = map.entrySet()
      .stream()
      .sorted(Comparator.comparing(entry -> -entry.getValue())) //desc order
      .toList()
      .get(1); // index start from 0

You can achieve it by collecting into TreeSet with a comparator by the Entry::getValue(). Poll last twice to get the 2nd largest result.

Map<String, Integer> map = Map.of(
		"Tom", 15,
		"Jerry", 17,
		"Silvester", 10,
		"Tweety", 12
);

NavigableSet<Map.Entry<String,Integer>> set = map.entrySet()
		.stream()
		.collect(Collectors.toCollection(
				() -> new TreeSet<>(Map.Entry.comparingByValue())));

Map.Entry<String,Integer> last = set.pollLast();                // Jerry=17
		Map.Entry<String,Integer> secondLast = set.pollLast();  // Tom=15

I'm surprised nobody has posted a simple O(n) solution:

import java.util.Map;
import java.util.HashMap;
import java.util.Map.Entry;
public class MyClass {
public static void main(String args[]) {
Map<String,Integer> map = new HashMap<>();
map.put("a",10);
map.put("b",12);
map.put("c",20);
map.put("d",18);
map.put("e",14);
map.put("f",16);
Entry<String, Integer> highest = null;
Entry<String, Integer> secondHighest = null;
for(Entry<String, Integer> entry:map.entrySet()) {
if(highest == null) {
highest = entry;
} else if(secondHighest == null) {
secondHighest = entry;
} else if(highest.getValue() <= entry.getValue()) {
secondHighest = highest;
highest = entry;
} else if(secondHighest.getValue() <= entry.getValue()) {
secondHighest = entry;
} else {
// ignore
}
}
System.err.println("Highest: " + highest.getKey() + ": " + highest.getValue());
System.err.println("Second highest: " + secondHighest.getKey() + ": " + secondHighest.getValue());
}
}

If you use a TreeMap, which is an implementation of Map, you can provide a comparator at the time of its creation to sort the data which is entered into it, automatically. In this way, you can directly fetch your desired result.