a) Sorting HashMap by value if you want only values Finally, the map is sorted according to its keys. HashMap, TreeMap etc. Sort HashMap by Key. Attention reader! brightness_4 November 17, 2020. 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In this example we will sort the values of the HashMap using TreeMap and Comparator. edit Author: Venkatesh - I love to learn and share the technical stuff. However, retrieving the values based on sorted keys is possible in below given ways. I want to sort by the key (project) and then display sorted key (project) and corresponding value (employee list). After that get the Set of elements from the Map and convert Set into the List. It provides the basic implementation of the Map interface of Java. Map mapSportsPersonality = new HashMap<>(). Key and Value can be of different types (eg – String, Integer). the value field from the key/value pair, HashMap based implementation is not thread safe. import java.util.ArrayList; import java.util.Collection; import If you want to make a mutable object as key in hashmap, then you have to make sure that state change for key object does not change the hash code of object. comparingByKey () returns a comparator that compares Map.Entry in natural order on key. It stores the data in the form of Key, Value pairs, where the keys must be unique but there is no restriction for values. close, link The method does not return any value. HashMap Class Methods in Java with Examples | Set 1 (put(), get(), isEmpty() and size()), Differences between HashMap and HashTable in Java, Differences between TreeMap, HashMap and LinkedHashMap in Java, Difference between HashMap and IdentityHashMap in Java, Java Program for Odd-Even Sort / Brick Sort, Java Program to Sort Vector Using Collections.sort() Method, Data Structures and Algorithms – Self Paced Course, Ad-Free Experience – GeeksforGeeks Premium, We use cookies to ensure you have the best browsing experience on our website. Don’t stop learning now. HashMap must synchronized externally, If multiple threads access a hashmap concurrently. We can sort HashMap on basis of value using the Comparator interface. To sort HashMap by key, we can use TreeMap class. Map.Entry. Please use ide.geeksforgeeks.org, As we know there is an implementation of NavigableMap interface, known as TreeMap which also holds a key value pair but maintains the key sorted (natural order) in ascending order by default.Hence, to sort a HashMap by it's key it is only required to convert existing HashMap into a TreeMap.Apart from this, we can also define our custom sort order by implementing … In this quick tutorial, we'll learn how to sort a HashMap in Java. 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