Java tutorial
//package com.java2s; import java.util.Map; import java.util.concurrent.ConcurrentHashMap; public class Main { public static <K, V extends Comparable> K getKeyOfMaxValue(ConcurrentHashMap<K, V> map) { Map.Entry<K, V> entry = map.reduceEntries(1000, (oldEntry, newEntry) -> { if (oldEntry.getValue().compareTo(newEntry.getValue()) > 0) return oldEntry; else return newEntry; }); return entry.getKey(); } }