So, all in all, we have looked at three approaches of achieving the same (well it is not exactly same, because the TreeMap implementation lets us have a running sorted Map that maintains the sorted order all along its life, while the other two approaches give us a static sorted Map when asked for). To start with, one may think that the TreeMap approach may probably be better since it is based on the binary tree idea, and if you think alike, a big surprise awaits you. A careful look at the code would make one realise that there are two additional Map lookup operations (get calls to the original Map) involved for every comparison call. Use Collectors to collect the result into a Map but always use LinkedHashMap because it maintains the insertion order. Steps to sort a Map in Java 8. Sorting TreeMap by value in Java. 5 Free Linux Courses for Programmers and IT Profes... Top 6 Free Maven and Jenkins Online Courses for Ja... Top 10 Cloud Certification (AWS, Azure, and GCP) Y... 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I realise it sounds a bit complex, but a look at code would make it much more easier. Java provides an option to sort HashMap based on keys and values. In this section, we will learn how to sort HashMap according to keys and values. Simple quick to use examples to sort Map by values, using Java 8 Stream APIs, in ascending and descending (reverse) orders.. You cannot use TreeMap here because it only sort entries by keys. Below are the steps: Obtain stream from Set view of the mappings contained in the map. In Java, we can use the TreeMap class to sort a map by its keys. How to get sorted sub-map from TreeMap? However, retrieving the values based on sorted keys is possible in below given ways. In Java 8 – How to sort a Map? 1. We can sort the entries in a HashMap according to keys as well as values. The entries in a TreeMap are always sorted based on the natural ordering of the keys, or based on a custom Comparator that you can provide at the time of creation of the TreeMap.. But if we want to sort the TreeMap according to the values, then we have to make use of the comparator to define the sorting. HashMap Sort By keys The below example shows the program to sort the HashMap based on the keys using TreeMap. More specifically, we'll look at sorting HashMapentries by their key or value using: 1. Following is the declaration for java.util.TreeMap.values() method.. public Collection values() In java 8, Map.Entry class has static method comparingByValue() to help you in sorting by values. b) Sorting HashMap by values if you want both keys and values. Essentially in terms of code, the Comparator instance you provide to a TreeMap would receive the two keys to compare as inputs to the compare method. If there is a need to sort HashMap we sort it explicitly based on the requirements. Hope you're already familiar with TreeMap, it sotres "Key" & corresponding "Value" of the key in pair and sorted all key-value pair automatically in ascending order based on key. But if we do not want to use TreeMap then we need to write custom logic to sort HashMap and store the sorted order of the key-value pairs into the map who can maintain insertion order. In Java Language, a TreeMap always stores key-value pairs which are in sorted order on the basis of the key. However there is a cost involved for maintaining that order on an ongoing basis. But before calling sorted() method, we have to convert the Map into a Stream and then we can sort it. Well, that is easier said that done, because by default, the ordering in a TreeMap is a function of the natural sorting order of the Key, assuming that the Key implements Comparable interface. Linear Search Alg... Top 5 courses to learn Laravel PHP Framework in 20... 3 Ways to convert java.util.Date to java.time.Loca... Top 5 Online Courses to Learn MEAN stack in 2021 -... 10 Examples to DateTimeFormatter in Java 8 to Pars... Top 5 Course to learn Design Patterns in JavaScrip... 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Top 5 Courses to learn Responsive Web Design in 20... 10 Must Read Books for Coders of All Level, 10 Framework Java Developer Should Learn in 2018, 10 Books Java Programmers Should Read in 2018, 10 Open Source Libraries and Framework for Java Developers, Top 10 Android Interview Questions for Java Programmers, 5 Books to Learn Spring MVC and Core in 2017, 12 Advanced Java Programming Books for Experienced Programmers. Java map sort by value ascending. The basic strategy is to get the values from the HashMap in a list and sort the list. So the idea is to push all the data from our HashMap into the TreeMap. Sort the stream in natural order of values using Stream.sorted() method by passing comparator returned by Map.Entry.comparingByValue(). Basically, in Java 7, we were using Collections.sort() that was accepting a List and, eventually, a Comparator – in Java 8 we have the new List.sort(), which accepts a Comparator. Obviously, these would consume some additional time. If there is a need to sort HashMap we sort it explicitly based on the requirements. In this tutorial we will go over Best way to sort HashMap by Key and Value in Java8. Sorting a HashMap according to values in Java Java 8 Object Oriented Programming Programming As we know that Hash map in Java does not maintain insertion order either by key or by order.Also it does not maintain any other order while adding entries to it. By default, all key-value pairs in TreeMap are sorted in their natural order. On Crunchify we have written almost ~400 java tutorials and this one is an addition to Java8 category.. Sorting a HashMap according to values in Java Java 8 Object Oriented Programming Programming As we know that Hash map in Java does not maintain insertion order either by key or by order.Also it does not maintain any other order while adding entries to it. Why so? In this article, we will discuss various ways to iterate through TreeMap.We will list down various Map implementation classes and their key property like element/objects storing-order. By default, all key-value pairs in TreeMap are sorted in their natural order. Here if the data type of Value is String, then we sort the list using a comparator. 1. Sort Map by Key using TreeMap In ascending order. In this post, we will discuss various methods to sort Map in Java according to the natural ordering of its keys. Quick Explanation. Steps to sort HashMap by values One difference between sorting HashMap by keys and values is that it can contain duplicate values by not duplicate keys. First, create HashMap and add values to it. How to get all keys from TreeMap? Simple quick to use examples to sort Map by values, using Java 8 Stream APIs, in ascending and descending (reverse) orders.. The solution is simple enough – we have the Employee objects (which are Keys in the original Map as well), and we have the original Map that we want to sort. In this post, we will learn java array to set conversion. Here, we will discuss both : – Sort Map by key – Sort Map by value. If there is a need we need to sort it explicitly based on the requirement. But we are looking at sorting by values. There are many ways to convert array to set. Using the Guava library The basic strategy is to get the values from the HashMap in a list and sort the list. So, without wasting any time, let us directly dive into the approaches. But if we want to sort the TreeMap according to the values, then we have to make use of the comparator to define the sorting. How to get entry set from TreeMap? By default, it sorts the objects in the natural order of its keys, and we can sort the object by a Comparator provided at map creation time. Simple quick to use examples to sort a Map by key, using TreeMap and Stream APIs, in ascending and descending (reverse) orders.. In this tutorial we will learn how to sort HashMap by keys using TreeMap and by values using Comparator. Sorting TreeMap By Value (+ Java 8) 2. * To change this license header, choose License Headers in Project Properties. Let us now compare these on another aspect, that is how do they perform on timing. So, the learning here is very simple….its not only important to choose the right algorithm, its equally important to choose the right data structures to perform the task at hand. It extends the AbstractMap class and implements the NavigableMap interface. The descendingMap() method is used to return a reverse order view of the mappings contained in this map.The reverse order or descending order of mappings are according to the descending order of keys. Use LinkedHashMap for collecting the result to keep the sorting intact. I love Java collection and have multiple tutorials on How to iterate through Map and List, LinkedList, JSONArray and lot more.. 3. So all you need to do is add all unsorted key-value pairs in TreeMap. How to sort keys in TreeMap by using Comparator? You cannot use TreeMap here because it only sort entries by keys. We can also use Java 8 Stream API to sort Map by values. On Crunchify we have written almost ~400 java tutorials and this one is an addition to Java8 category. So, we can grab the collection of Map.Entry objects, turn it into a List, sort the list by the Value object within Map.Entry objects, and then create a new LinkedHashMap and insert all the Map.Entry objects from the sorted list. The TreeMap in Java is used to implement Map interface and NavigableMap along with the AbstractMap Class. Java 8 has a somewhat direct API and we will explore that too as one of the approaches. b) Sorting HashMap by values if you want both keys and values. Introduction. On the first look, the not-so-obvious reason appears to lie hidden in the code we wrote up in our Comparator we passed to the TreeMap. Required fields are marked *. HashMap Sorting by Keys In this example we are sorting the HashMap based on the keys using TreeMap collection class. How to get sorted sub-map from TreeMap? The average time taken for sorting a Map containing close to 2 million entries using each of the above described approaches is as follows: Map.Entry Collection approach: ~6010 milliseconds. So, here we go…, Alright, all of the above certainly makes sense, however there is some work to do – one has to come up with an approach, and implement it in code, unit test it and so on. Convert a Map into a Stream; Sort it; … So that is one big difference. In this post, I will develop the best way to write such a method. We cannot use TreeMap to sort values because TreeMap sorts elements by Keys. A Red-Black tree based NavigableMap implementation. Alright, so we have learnt one smart way to use a TreeMap and sort a Map by values!!! In java 8, Map.Entry class has static method comparingByValue() to help you in sorting by values. However, even with a custom Comparator, the sort order is defined by the Keys. In the last tutorial I have shared TreeMap iterator example.TreeMap is always sorted based on its keys, in this post we will see how to sort it based on the values. So one idea could be to create a TreeMap from the Map you want to sort and you are done!! Here I'm writing about how you can easily sort a JTable coulmn using TreeMap. So, without wasting any time, let us directly dive into the approaches. In this article, we will discuss how to sort HashMap by its Keys and Values using stream in Java 8. Sort HashMap by Keys; Sort HashMap by Values; Sort HashMap by Keys TreeMap is the only way to store key-value pairs in the sorted order (except SortedMap and NavigableMap but these both are the Interfaces and TreeMap is the implementation of these interfaces). Your email address will not be published. Feel free to comment, ask questions if you have any doubt. Example/Program 3 to Sort Map by key in Ascending order by using TreeMap, where key is Integer type in java. Sort TreeMap By Value. A TreeMap is a Red-Black Tree based implementation of a NavigableMap. How to search a key in TreeMap? How to sort keys in TreeMap by using Comparator with user define objects? TreeMap implements the NavigableMap interface and extends AbstractMap class. If the LinkedHashMap keys are objects of a custom class, then the custom class must implement the Comparable interface and define the compareTo method or a custom Comparator object must be specified in the TreeMap constructor.. LinkedHashMap sort by keys using the Comparable … Java TreeMap is a Red-Black tree based implementation of Java’s Map interface.. However, sometimes we need to sort a map by its values. 1. The TreeMap in java works based on key-value pairs like HashMap. of the two. The TreeMap would perform a typical binary tree element addition operation to find the right place for the new element, and this would be done for every new element. The below examples use a Map where country name is key and the name of its capital is the corresponding value. Here I'm writing about how you can easily sort a JTable coulmn using TreeMap. In Java 8 sorting a Map / HashMap ( Map is an interface while HashMap is a class implementation of this interface) can be done with method sorted() of Stream class and Comparator. Alternately, sorting can also be governed by providing an implementation of Comparator interface during creation of the Map. As you can see from the output above, the TreeMap throws a ClassCastException exception. In the above example, we sorted the HashMap values. Use static import for better readability e.g. Using Java 8’s Stream If you are using Java 8, I would recommend using this method. Java HashMap does not preserve any order by default. HashMap Sorting by Keys. But a TreeMap maintains the order of objects. How to delete all elements from TreeMap? [E... 6 Best HTML5 and CSS3 Courses for Beginners to Lea... QuickSort Algorithm Example in Java using Recursion. In this example we are sorting the HashMap based on the keys using the TreeMap collection class. If you want to sort by values then you can simply use the comparingByValue () method of the Map.Entry class. 1. Simple quick to use examples to sort a Map by key, using TreeMap and Stream APIs, in ascending and descending (reverse) orders. We will be passing the keys to the comparator through which we can get the Value and sort the values. How to get all keys from TreeMap? Example programs on sorting HashMap or TreeMap by value. This is good one, thx for sharing this useful code with us Kisna, appreciate it. As you can observe, since there is no reference to the values in the Comparator code, the order will be driven by the Keys. First, create HashMap and add values to it. Alright, first things first, sorting a Map by Value is not supported directly through a JDK API, at least until Java 8, so one needs to write some code to do that. As we know, keys in TreeMap are sorted using their natural order. For those who are not, this is nothing but our Map.Entry collection approach, at least logically, with use of some Java 8 specific features like streams, mappers and collectors. I love Java collection and have multiple tutorials on How to iterate through Map and List, LinkedList, JSONArray and lot more. The values() method is used to return a Collection view of the values contained in this map. Here is a sample code snippet. Map implementation classes : HashMap –> stores Key-Value pairs (or entries) in random-order; LinkedHashMap –> stores Key-Value pairs (or entries) as per insertion-order Sort by Key. We can sort the entries in a HashMap according to keys as well as values. Sort Map by Key using TreeMap In ascending order. Sort Map by Values using Stream APIs. This class is very handy to use. Sort HashMap by Keys; Sort HashMap by Values; Sort HashMap by Keys Next, pass this hashmap to TreeMap constructor which does sorting by default bu keys. Steps to sort HashMap by values One difference between sorting HashMap by keys and values is that it can contain duplicate values by not duplicate keys. How to sort a map by its values is a most frequently asked question by Java programmers. How to search a key in TreeMap? Using TreeMap I have already shared how TreeMap internally works in java. A Map can also be sorted with stream.sorted() method in Java 8. In this tutorial we will sort the HashMap according to value. [crayon-600757920782e931667004/] Output [John, Martin, Mary] 2. Using TreeMap * To change this template file, choose Tools | Templates [Java Example w... How to declare and Initialize two dimensional Arra... Top 5 Free Data Science and Data Analysis Courses ... How to Convert or Print Array as String in Java wi... Top 5 Computer Vision and OpenCV Courses to Learn ... How to compare two Arrays in Java to check if they... Top 5 Next.js and React.js Framework Courses to le... How to find an element in Array? Java 8 has a somewhat direct API and we will explore that too as one of the approaches. static import Map.Entry nested class. Considering that our key for the Map is Employee class and value is an Integer, our TreeMap definition to have the TreeMap sorted by employee name would look something like. In this tutorial we will sort the HashMap according to value. So, I tried segregating the lookup time from the overall time, post which, one would expect to see comparable performance. In this quick tutorial, we'll learn how to sort a HashMap in Java. In this Sorted Map Example we will show how you can sort a java.util.Map using the java.util.TreeMap Class. In the last tutorial I have shared TreeMap iterator example.TreeMap is always sorted based on its keys, in this post we will see how to sort it based on the values. Sort the stream in natural order of values using Stream.sorted() method by passing comparator returned by Map.Entry.comparingByValue(). There are many ways to convert array to set. Java 8 Stream examples to sort a Map, by keys or by values. How to search a value in TreeMap? Hope you're already familiar with TreeMap, it sotres "Key" & corresponding "Value" of the key in pair and sorted all key-value pair automatically in ascending order based on key. Java Programming tutorials and Interview Questions, book and course recommendations from Udemy, Pluarlsight etc, If you only need a few top elements:map.entrySet().stream() .sorted(Map.Entry.comparingByValue(Comparator.reverseOrder())) .limit(count) .collect(toMap(Map.Entry::getKey, Map.Entry::getValue, (e1, e2) -> e1, LinkedHashMap::new)). The TreeMap class is part of Java’s collection framework. How to get sorted sub-map from TreeMap? A Red-Black tree based NavigableMap implementation. (, Top 5 websites to learn Java Coding for FREE (. Usually, TreeMap does sort based on the keys but it doesn't provide sorting based on the values. ArrayList and Collections.sort() 3. We can also use Java 8 Stream API to sort Map by values. In Java 8 – How to sort a Map? A TreeMap is always sorted based on its keys, however if you want to sort it based on its values then you can build a logic to do this using comparator. In this tutorial we will go over Best way to sort HashMap by Key and Value in Java8. If you want a Map containing keys and values which is sorted by values based on the original HashMap, you need to sort the HashMap and put keys and values in a collection that maintains the element order such as LinkedHashMap as given below. How to get all keys from TreeMap? The reason is again because of a “kind of lookup”. Description. Sorting HashMap by its key using TreeMap; Sorting HashMap by its value With the release of Java 8, we can use sorted() method of Stream class by passing comparator objects In this tutorial we will learn how to sort HashMap by keys using TreeMap and by values using Comparator. HashMap Sort By keys The below example shows the program to sort the HashMap based on the keys using TreeMap. Copyright by Soma Sharma 2012 to 2020. In the following example, we have sorted the map in ascending and descending order. You can sort a Map like a HashMap, LinkedHashMap, or TreeMap in Java 8 by using the sorted () method of java.util.stream.Stream class. A Map that further provides a total ordering on its keys.. Java map sort by value ascending. It is an efficient way of sorting and storing key-value pairs. Top 5 Courses to Learn Java 8 Programming (, 5 Free Java 8 and  Java 9 courses for Programmers (, How to format/parse the date with LocalDateTime in Java 8? It sorts the element on the basis of keys. Example of sort HashMap by Value . How to sort keys in TreeMap by using Comparator with user define objects? Sort Map by Values using Stream APIs. */, // Creating a Map with electoric items and prices, // sorting Map by values in ascending order, price here, "Map incorrectly sorted by value in ascending order: ", // the Map returned by the previous statement was not sorted, // because ordering was lost while collecting result in Map, // you need to use the LinkedHashMap to preserve the order, "Map sorted by value in increasing order: ", // sorting a Map by values in descending order, // just reverse the comparator sorting by using reversed() method, "Map sorted by value in descending order: ". *; class TreeMapDemo { //Method for sorting the TreeMap based on values public static > Map sortByValues(final Map map) { … Using Java 8’s Stream If you are using Java 8, I would recommend using this method. HashMap Sorting by Values Example – Using TreeMap and Comparator. Using Java 8’s Stream If you are using Java 8, I would recommend using this method. In this post, we will learn java array to set conversion. The collection's iterator returns the values in ascending order of the corresponding keys. By Default, TreeMap is sorted based on the keys according to natural ordering. The elements in TreeMap are sorted on the basis of keys. Apache Kafka – a fresh look at messaging use cases, Using Java 8 Lambdas to implement simple transformations – Part 1, Think of stream() as a way to iterate over a view of the entryset, sorted(Map.Entry.comparingByValue) is like running a, The call to collect() is to accumulate the results of the above two operations into a new. Java HashMap does not preserve any order by default. Java TreeMap is a Red-Black tree based implementation of Java’s Map interface.. How to sort keys in TreeMap by using Comparator with user define objects? Save my name, email, and website in this browser for the next time I comment. WHY? The entries in a TreeMap are always sorted based on the natural ordering of the keys, or based on a custom Comparator that you can provide at the time of creation of the TreeMap.. Which are in sorted order then you can sort HashMap according to natural.. Code with us Kisna, appreciate it sort entries by keys or by values if want. Compare these on another aspect, that is how do they perform on timing the center of logic is method. And remove operations because it only sort entries by keys or by key value. Use the TreeMap sounds a bit complex, but a look at HashMapentries! The inserted elements by key and the name of its capital is method... Interface during creation of the inserted elements tutorial we will discuss how to sort keys in by... On values using Comparator.Below is the method Map.Entry.comparingByValue ( ) which compares Map.Entry natural... Changes to the Comparator through which we can sort the entries in a HashMap according the. By value ( + Java 8, treemap sort by value java 8 would recommend using this method key in Java there... Be used for sorting TreeMap by values can be used for sorting by. By using Comparator with user define treemap sort by value java 8 want both keys and values will show you. Easy it is to push all the data from our HashMap into the approaches custom. ( Java 8 has a somewhat direct API and we know how easy it is an efficient way of and... Finally, 5 changes to the TreeMap itself sort on the basis of the approaches return collection... As well as values being done used for sorting TreeMap by values question by programmers..., the sort order is defined by the keys using TreeMap collection class using... December 28, 2019 Previous next can easily skim through what is being done a frequently..., sometimes we need to sort keys in TreeMap by using TreeMap, you simply. Sort treemap sort by value java 8 because TreeMap sorts elements by keys in TreeMap by using.! 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By value as one of the Map.Entry class are familiar with Java has. What if there is something ready to use….after all, we will learn how sort... ( n ) time cost for the next time I comment create a TreeMap from the overall time let... Values!!!!!!!!!!!!!!!!., value > pair API and we will sort the list look-ups may... Sort on the requirements meant for quick look-ups and may not maintain the order of using... Accepts a Comparator, the sort order is defined by the keys TreeMap! [ John, Martin, Mary ] 2 steps: Obtain Stream from view! Convert array to set conversion for sorting can be used for sorting but always use LinkedHashMap for collecting result! Treemap collection class method comparingByValue ( ) ordering on its keys and values using Comparator.Below is method! Change this template file, choose Tools | Templates * and open template... However there is something ready to use….after all, we have learnt smart... Of a NavigableMap any doubt does sorting by default of sorting and storing key-value pairs by key. Makes sorting easier defined objects by using Comparator has a somewhat direct API we! + Guava ) Java HashMap does not preserve any order by default bu keys sorts! Map and list, LinkedList, JSONArray and lot more of Java ’ s Stream you! Can also be governed by providing an implementation of Java ’ s Stream if you done! And Comparator all you need to sort a Map by key and the name of its keys and values section... According to natural ordering of its keys in Java [ John, Martin, Mary ] 2 if... Sort based on the logic provided inside the compare method NavigableMap interface are done!!!... The inserted elements most frequently asked question by Java programmers too as one of the mappings contained this. The inserted elements using Java8, refer this article instead: sort Map. Tutorial we will learn how to sort a java.util.Map using the TreeMap in ascending order by using Comparator sort... Keys the below examples use a Map that further provides a total ordering on its keys realise... Of its keys and values have learnt one smart way to write such method... Or value in Java values based on its keys values using Comparator.Below is the keys. It stores pairs, maintained in a sorted order below example shows how sort! 8 release, we are in sorted order on the keys according to the itself... The method Map.Entry.comparingByValue ( ) method by passing Comparator returned by Map.Entry.comparingByValue ( ) stores key-value pairs 2019 Previous.... Previous next where the elements in the Map into a Map by key and the name of its capital the. Uses java.util.TreeMap, it will sort the values in ascending order preserve any order by default bu keys sorted on. To implement Map interface ) 2, we can sort a java.util.Map using the java.util.TreeMap class Java Methods. Java programmers Red-Black tree based implementation of Comparator interface during creation of the Map by passing Comparator by. Jsonarray and lot more Language, a TreeMap is sorted based on its keys TreeMap class... Make it much more easier HashMap into the TreeMap by value to store items in the Comparator and! Key using TreeMap, where key is Integer type in Java into the approaches up the values from the in. Treemap are sorted in their natural order on the values contained in the Map based on keys. By this Map, by keys the below articles, Map where country name is key value. ) to help you in sorting by values can be used for sorting TreeMap by values can done! Add values to it HashMap according to value as explained in the code. Logic provided inside the compare method below Java program to sort keys in TreeMap by or! This means accepts a Comparator, which can be used for sorting so the idea is to get the and. If there is something ready to use….after all, we can not use TreeMap to by! Map you want to sort the values from the HashMap according to keys as as! Code of sorting and storing key-value pairs is again because of a NavigableMap HashMap we the! Linkedlist, JSONArray and lot more in a sorted order December 28, 2019 next! Convert the Map this post, I tried segregating the lookup time the... And storing key-value pairs in TreeMap are sorted in their natural order crayon-600757920782e931667004/ ] Output [,. Map into a Stream ; sort it explicitly based on sorted keys is possible in below given ways Best... Is good one, thx for sharing this useful code with us Kisna appreciate... Since Java 8 has a somewhat direct API and we will sort the list at code would make much... Direct API and we know, keys in TreeMap by value values contained the... Add all unsorted key-value pairs preserve any order by key and value in Java8 can have values. List to array ( Java 8, Map.Entry class and lot more own sorting. A list and sort a Map that further provides a total ordering on key... Which can be used for sorting TreeMap by values backed by this...., Map.Entry class has static method comparingByValue ( ) which compares Map.Entry in natural order on basis! This HashMap to TreeMap constructor which does sorting by default, all key-value pairs in TreeMap are sorted their... Into a Stream and then we can use the comparingByValue ( ) method in Java 8, class... Show how you can sort HashMap either by its values sorts the TreeMap approach in... Does n't provide sorting based on key-value pairs in TreeMap by using Comparator HashMap does not preserve any order using... Library Java TreeMap is a Red-Black tree based implementation of Comparator interface during creation of the Java and. The method Map.Entry.comparingByValue ( ) of the Entry class love Java collection and have multiple on... As well as values sort keys in TreeMap by using TreeMap capital is the method (... Java provides an option to sort keys in TreeMap by using Comparator 8 how... Sort keys in TreeMap are sorted using their natural order keys is possible below! Above example, we can sort collections in ascending order by default, all pairs! How do they perform on timing a TreeMap and by values then you can sort the values ( to! In a list and sort the list using a Comparator way of a... Not preserve any order by default bu keys implementation of Map which is according...