Java 8 Stream - How to Sort a Map using lambda | Example | Java Techie

This video explain you How to sort a Map in java 8 using lambda expression and stream API even we use Comparator for custom sorting order with stream api - real time example
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[@venkatah9847]

Thanks for the good explanation. The way examples were explained is awesome. Please continue to do the same.

[@omsonschicago5872]

Thank you so much. Learning from your videos in realtime.

[@nidhimanav311]

First of all ... I am really thankful to you ... You explained every topic i.e. spring ,java8 or others with explanatory way. It will be quite easy for us to understand the topic. Aapko guru dakshina to dena bnta h 🙏

[@Javatechie]

Thank you so much for your word. Glad to hear this keep learning 😃

[@sreetmi1918]

You are going all the way....Really very useful java material online ...far far better than Institutes who demand money and does no justice in teaching java....Thank you buddy

[@Javatechie]

Thank you so much for appreciating it. Keep learning buddy 🙂

[@madhurajsingh6558]

Best explanation. I learnt a lot from this channel. Thank you so very much 🙏

[@Javatechie]

Good to hear this Madhuraj . Keep learning

[@siyedyoussef3202]

Great video as always 👍👍👍👍

[@francescalabonte4346]

Absolutely great. thank you.

[@ramkethireddy9445]

great presentation with realtime examples!! please also cover Optional Class methods

[@YanivNahumIPN]

Very nice explanation. Regards from Mexico.

[@Mohamed-uf5jh]

Super Great Excellent explain

[@vinitgawali1]

Thanks you cleared all my doubts

[@shubhamthakare5229]

Amazing explanation! Please make more video on java 8

[@ILuvBilli]

Super Great Excellent

[@sreerekhamenon1164]

Good explanation.. thanks

[@neutral911]

I've never seen this kind of detailed explanation on rare concepts. Very useful bro... Thank You so much for this video.. Keep it up :)

[@Javatechie]

Thanks KodandaRam . Good to hear this

[@vijayr6540]

Thankyou nice explanation

[@jagrutipatil1020]

You are genuine...🥰

[@taufiquealam4125]

Great....God bless you.....Could you please make video on difference between interface and abstract class with example in Java 8. Would be highly appreciated.

[@lifeofvillageculture628]

tq for doing this vedio, its useful.

[@raghukg4]

Hello Java Techie, your explanation is the best ever. My request is that please make a video for Optional class as well. Thanks.

[@Javatechie]

Okay I will do it

[@sreddy8141]

Sir , found very late, but so helpful, please do videos on data structures and algorithm with same kinda explanation for time and space complexity

[@akhileshyaduwanshi6008]

Great Tutorial

[@Vishal-8995]

Mr Dependable 🙌🏼

[@kishordige4654]

Thank you very much!

[@gamerauto]

Let me Zum it guys, thanks man!

[@ashmpatel]

Nice tutorial

[@saurabhkailashchandrapuran8609]

Please don't stop here .. make more videos on this type of concept.

[@Javatechie]

Okay we will continue java 8 stream API more features

[@aakashkumbhare4399]

Covered most of my doubts

[@MuraliM.A.]

Thanks for the video

[@Explorewith4x4]

NYC information❤

[@abhinandeshwar6335]

Best video

[@rachanabr]

thankyou

[@sarojsahoo8763]

Instead of using reverse() on comparingByvalue I have used like below .. dataMap.entrySet().stream().sorted(Map.Entry.comparingByValue(Comparator.reverseOrder())).forEach(System.out::println);

[@Javatechie]

If your value contains some custom object then it won't work .

[@RealSlimShady-um6gf]

@Sarojsahoo yes your code is an alternative to primitive datatype if used. I would be interested in the time complexity of both the approaches.

[@yared555]

Nice one , I want to see how to debbug in java

[@Javatechie]

Okay I will show with intelij

[@RealSlimShady-um6gf]

This example too you used (int) for Long. If you use actual Long values then this code will break. Very fuzzy logic to use Employee as key and value as Integer

[@uxiraj]

It took me a while to understand that he used a list to stream list of strings and then map to stream employee objects

[@sujithg5873]

Can u detailed explanation for method reference

[@tiejeevan]

I feel this hard as hell even though I practice a lot

[@dupindersingh1599]

When will you upload more videos related to Java Stream API

[@tiwarybaba]

sorry for the lame question...but we're using the entrySet() with employeeMap just to get it in list form(Map.Entry), so that we can use it for sorting, like entry.getKey()... right?

[@Javatechie]

No you need to use Map.Entry.comparingByKey()

[@tiwarybaba]

@@Javatechie that I understood...my question is with the Map reference (employeeMap) in the example, u used employeeMap.entrySet()...why did u did that?

[@lifeisbeautiful230]

Line number 21gives Cannot infer type arguments for ArrayList error. I am using Java 17.

[@Javatechie]

Share the code snippet please

[@lifeisbeautiful230]

@@Javatechie //THIS LINE IS HAVING ERROR "gives Cannot infer type arguments for ArrayList " //I am using Java 17 List entries = new ArrayList(imap.entrySet()); Collections.sort(entries, new Comparator() { @Override public int compare(Entry o1, Entry o2) { // TODO Auto-generated method stub return o1.getKey().compareTo(o2.getKey()); } }); for(Entry entry:entries) { System.out.println(entry.getKey()+""+entry.getValue()); } }

[@acchutdevkule7841]

Hello, how can wirite program for passing employee object in hashmap as value and want to sort by value based on employee id?

[@Javatechie]

I already explained it just change syntax to comparingByValue instead of comparingByKey

[@geetha.egowda8674]

I am doing the same way, but i am getting an error like LinkedHashMap cannot be cast to class ProcessFlow (POJO) (LinkedHashMap is in java.base of loader 'bootstrap' ; ProcessFlow is in unnamed module of loader 'app'). I am stuck, can you please help here

[@abhinavjain5584]

Time stem 6:54 i try to add reversed() method but it gives error

[@pankajpandey6298]

Hi Sir can you tell how to collect map object using stream instead of sysout?

[@Javatechie]

Just use collect(Collectors.toList()) instead of foreach

[@pankajpandey6298]

@@Javatechie thankyou sir

[@sreddy8141]

i have tried the same but its not sorting not sure whats the issue

[@krishnamohan5771]

can we remove the comparator in the treemap constructor if we are sorting by streams

[@Javatechie]

Yes comparator not required to explicitly added in constructor if you are using stream

[@krishnamohan5771]

@@Javatechie its giving class cast exception if no comparator is provided for tree map constructor

[@swacharahman5084]

Hello, what to do if the map's key and value are both integer?

[@Javatechie]

How does it matter? Based on either key or value you can easily sort right

[@swacharahman5084]

@@Javatechie yes, i figured that out. btw wonderful video,THANK YOU

[@user-uf7uq3wg3j]

sir ClassCastException is coming when i am not passing lamda exp in TreeSet Constructor . when we are sorting using streams why i need to still pass lamda exp in TreeSet Constructor???

[@Javatechie]

Lambda internally uses HashSet not TreeSet buddy

[@user-uf7uq3wg3j]

@@Javatechie sir Sorry,i didn't understand what you are saying 😅😅

[@Javatechie]

Share me the code where you are getting exception

[@user-uf7uq3wg3j]

@@Javatechie public class SortMap2 { public static void main(String[] args) { Map employeeMap = new TreeMap(); employeeMap.put(new Employee(176, "Roshan", "IT", 600000), 60); employeeMap.put(new Employee(388, "Bikash", "CIVIL", 900000), 90); employeeMap.put(new Employee(470, "Bimal", "DEFENCE", 500000), 50); employeeMap.put(new Employee(624, "Sourav", "CORE", 400000), 40); employeeMap.put(new Employee(284, "Prakash", "SOCIAL", 1200000), 120); System.out.println(employeeMap); employeeMap.entrySet().stream().sorted(Map.Entry.comparingByKey(Comparator.comparing(Employee::getSalary).reversed())) .forEach(System.out::println); } }

[@jeet2450]

Could you plese help me to sort like this Map using java 8

[@Javatechie]

Jeet send me the sample collection and Expected order please

[@jeet2450]

@@Javatechie Map [aaaaaa, rrt]=[TestDTO(modelCode=aaaaaa, modelTypeCode=rrt, colourCode=389...), TestDTO(modelCode=aaaaaa, modelTypeCode=rrt, colourCode=30..), TestDTO(modelCode=aaaaaa, modelTypeCode=rrt, colourCode=308.) [zkaka, rrt]=[TestDTO(modelCode=zkaka, modelTypeCode=rrt, colourCode=389...), TestDTO(modelCode=zkaka, modelTypeCode=rrt, colourCode=30..), TestDTO(modelCode=zkaka, modelTypeCode=rrt, colourCode=667.) [ckaka, rrt]=[TestDTO(modelCode=ckaka, modelTypeCode=rrt, colourCode=389...), TestDTO(modelCode=ckaka, modelTypeCode=rrt, colourCode=30..), TestDTO(modelCode=ckaka, modelTypeCode=rrt, colourCode=667.) Modelcode and modelTypeCode is same in the key. Key--> [aaaaaa, rrt] based on key please sort the map.

[@sujitkumarmishra8004]

Hi Basant, map.entrySet().stream().sorted(Map.Entry.comparingByKey().reversed()).forEach(System.out::println); In the above line, reversed() method is not working. I am getting compile time error here in this case. But when I am trying the below approach, it's working. map.entrySet().stream().sorted(Entry. comparingByKey().reversed()).forEach(System.out::println); Please suggest exactly in which way we have to try?

[@Javatechie]

We need to use collections.reverse please check out my java 8 programming questions i have explained there

[@RealSlimShady-um6gf]

13.05 also used reversed. Didn't understand the logic of using String and Integer. Basant used String and Integer initially just to explain and later he shifted to a custom Employee class which is debatable

[@ramesh_p]

@@Javatechie This may work by adding explicitly the type of comparator returned by comparingByKey(). Something like this map.entrySet().stream().sorted(Map.Entry.comparingByKey().reversed())

[@kanagujagan509]

How to sort more than one properties.?

[@rahulben4762]

entries.stream().sorted(Map.Entry.comparingByKey().reversed()).forEach(System.out::println); is not working at 6:53 please help

[@Javatechie]

Is reversed method not applicable for sorted .I believe I show it .if not let me know

[@rahulben4762]

​@@Javatechie employeeMap.entrySet().stream().sorted(Map.Entry.comparingByValue(Comparator.comparing(Employee::getDept).reversed())).forEach(System.out::println); So Basant Map.Entry.ComparingByKey is working but Map.Entry.ComparingByValue in combination of reversed() method. Thank you in advance

[@Javatechie]

@@rahulben4762 its working dude please try with same syntax which i share in video employeeMap.entrySet().stream() .sorted(Map.Entry.comparingByKey(Comparator.comparing(Employee::getDept).reversed())) .forEach(System.out::println);

[@Javatechie]

@@rahulben4762 for value we can try below poc , i didn't find any straight forward approach employeeMap.entrySet() .stream() .sorted(Collections.reverseOrder(Map.Entry.comparingByValue())) .collect( toMap(Map.Entry::getKey, Map.Entry::getValue, (e1, e2) -> e2, LinkedHashMap::new));

[@venuvamsi5344]

Sir,If we have to use object as key in hash map then Do we need to overide equals and hashcode? If yes,what are problems do we face without overiding?

[@krishnamohan5771]

why you are using treemap here..any reason

[@Ankit-vp7nt]

Comparing by value how to do ...

[@Javatechie]

Already explained in this video please have a look

[@Ankit-vp7nt]

@@Javatechie Map map= EmpDataBase.getEmployee(); //traditional apporch List entries=new ArrayList(map.entrySet()); Collections.sort(entries,(o1,o2) -> o1.getValue().getId()-o2.getValue().getId()); for(Entry entry:entries) { System.out.println(entry); } Bro in this way working comparing by value

[@Ankit-vp7nt]

But using stream map.entrySet().stream().sorted(Map.Entry.comparingByValue(new Comparator() { @Override public int compare(Entry o1, Entry o2) { return o1.getValue().getId()-o2.getValue().getId(); } })); I stuck

[@Ankit-vp7nt]

Help me bro

[@Ankit-vp7nt]

Bro working just Chech it correct or not map.entrySet().stream().sorted((o1,o2) -> o1.getValue().getId()-o2.getValue().getId()).forEach(System.out::println);

[@AmritAgarwal07]

HashMap keyValuePairs = new HashMap(); var valuesList = keyValuePairs.Where(x => x.Value == keyValuePairs.Values.Max()).Select(v => v.Key).OrderBy(y => y).ToList();

[@AmritAgarwal07]

can you tell me the equivalent Java stream code for this?

[@Javatechie]

Let me check

[@AmritAgarwal07]

@@Javatechie ok

[@alldemb9496]

// Sort map by values using stream Map myMap1 = new HashMap(); myMap1.put("a", 1); myMap1.put("d", 2); myMap1.put("b", 3); myMap1.put("f", 4); myMap1.put("h", 0); myMap1.put("g", 4); myMap1.put("e", 8); Map employeeMap = new HashMap(); employeeMap.put(5, new Employee(1, "Tom", 20)); employeeMap.put(9, new Employee(9, "Robert", 45)); employeeMap.put(1, new Employee(100, "Gita", 29)); employeeMap.put(6, new Employee(15, "Tara", 25)); employeeMap.put(3, new Employee(3, "Bal", 29)); employeeMap.put(2, new Employee(22, "Tarun", 39)); // Sorting using comparator //myMap1.entrySet().stream().sorted((a,b)->a.getKey().compareTo(b.getKey())).forEach(System.out::println); //myMap1.entrySet().stream().sorted((a,b)-> a.getValue()-b.getValue()).forEach(System.out::println); // Reverse order //myMap1.entrySet().stream().sorted((a,b)->b.getKey().compareTo(a.getKey())).forEach(System.out::println); //myMap1.entrySet().stream().sorted((a,b)-> b.getValue()-a.getValue()).forEach(System.out::println); // Objects //By age //employeeMap.entrySet().stream().sorted((a,b)->a.getValue().getAge()-b.getValue().getAge()).forEach(System.out::println);; //By name //employeeMap.entrySet().stream().sorted((a,b)->a.getValue().getName().compareTo(b.getValue().getName())).forEach(System.out::println);

[@kishyash1]

Hi Java Technie map.entrySet().stream().sorted(Map.Entry.comparingByKey().reversed()).forEach(System.out::println); above code showing compilation error because of reversed method above map is string as key and int as value

[@RN-jo8zt]

Do we really need stream for sorting? I can write like below studentslist.sort( (o1, o2) -> o1.getFirstName().compareTo(o2.getFirstName()));

[@Javatechie]

Why lambda and functional interface introduced?

[@RN-jo8zt]

I rhink we can use it on collection framework for better performance and code will be short and flexible

[@Javatechie]

Correct when I am doing sorting here . I am just doing it for collections of objects