Sorting HashMap by values

Question

I need to sort my HashMap according to the values stored in it  The HashMap contains the contacts name stored in phone   Also I need that the keys get automatically sorted as soon as I sort the values  or you can say the keys and values are bound together thus any changes in values should get reflected in keys   HashMap lt Integer String gt  map   new HashMap lt Integer String gt     map put 1  froyo    map put 2  abby    map put 3  denver    map put 4  frost    map put 5  daisy      Required output   2 abby  5 daisy  3 denver  4 frost  1 froyo

User · Answer

I extends a TreeMap and override entrySet() and values() methods. Key and value need to be Comparable.

Follow the code:

public class ValueSortedMap<K extends Comparable, V extends Comparable> extends TreeMap<K, V> {

    @Override
    public Set<Entry<K, V>> entrySet() {
        Set<Entry<K, V>> originalEntries = super.entrySet();
        Set<Entry<K, V>> sortedEntry = new TreeSet<Entry<K, V>>(new Comparator<Entry<K, V>>() {
            @Override
            public int compare(Entry<K, V> entryA, Entry<K, V> entryB) {
                int compareTo = entryA.getValue().compareTo(entryB.getValue());
                if(compareTo == 0) {
                    compareTo = entryA.getKey().compareTo(entryB.getKey());
                }
                return compareTo;
            }
        });
        sortedEntry.addAll(originalEntries);
        return sortedEntry;
    }

    @Override
    public Collection<V> values() {
        Set<V> sortedValues = new TreeSet<>(new Comparator<V>(){
            @Override
            public int compare(V vA, V vB) {
                return vA.compareTo(vB);
            }
        });
        sortedValues.addAll(super.values());
        return sortedValues;
    }
}

Unit Tests:

public class ValueSortedMapTest {

    @Test
    public void basicTest() {
        Map<String, Integer> sortedMap = new ValueSortedMap<>();
        sortedMap.put("A",3);
        sortedMap.put("B",1);
        sortedMap.put("C",2);

        Assert.assertEquals("{B=1, C=2, A=3}", sortedMap.toString());
    }

    @Test
    public void repeatedValues() {
        Map<String, Double> sortedMap = new ValueSortedMap<>();
        sortedMap.put("D",67.3);
        sortedMap.put("A",99.5);
        sortedMap.put("B",67.4);
        sortedMap.put("C",67.4);

        Assert.assertEquals("{D=67.3, B=67.4, C=67.4, A=99.5}", sortedMap.toString());
    }

}

User · Answer

In Java 8   Map lt Integer  String gt  sortedMap         unsortedMap entrySet   stream        sorted Entry comparingByValue         collect Collectors toMap Entry  getKey  Entry  getValue                                 e1  e2  - gt  e1  LinkedHashMap  new

User · Answer

package com naveen hashmap   import java util    import java util Map Entry   public class SortBasedonValues                    param args             public static void main String   args             HashMap lt String  Integer gt  hm   new HashMap lt String  Integer gt             hm put  Naveen   2           hm put  Santosh   3           hm put  Ravi   4           hm put  Pramod   1           Set lt Entry lt String  Integer gt  gt  set   hm entrySet            List lt Entry lt String  Integer gt  gt  list   new ArrayList lt Entry lt String  Integer gt  gt                   set           Collections sort list  new Comparator lt Map Entry lt String  Integer gt  gt                  public int compare Map Entry lt String  Integer gt  o1                      Map Entry lt String  Integer gt  o2                    return o2 getValue   compareTo o1 getValue                                        for  Entry lt String  Integer gt  entry   list                System out println entry getValue

User · Answer

found a solution but not sure the performance if the map has large size  useful for normal case                 sort HashMap lt String  CustomData gt  by value        CustomData needs to provide compareTo   for comparing CustomData         param map              public void sortHashMapByValue final HashMap lt String  CustomData gt  map            ArrayList lt String gt  keys   new ArrayList lt String gt             keys addAll map keySet             Collections sort keys  new Comparator lt String gt                   Override             public int compare String lhs  String rhs                    CustomData val1   map get lhs                   CustomData val2   map get rhs                   if  val1    null                        return  val2    null    1   0                    else if  val1    null   amp  amp   val2    null                         return   val1 compareTo val2                                     else                       return 0                                                       for  String key   keys                CustomData c   map get key               if  c    null                    Log e  key   key    CustomData   c toString

User · Answer

public static TreeMap lt String  String gt  sortMap HashMap lt String  String gt  passedMap  String byParam        if byParam trim   toLowerCase   equalsIgnoreCase  byValue                 Altering the  key  value  - gt   value  key          HashMap lt String  String gt  newMap    new HashMap lt String  String gt             for  Map Entry lt String  String gt  entry   passedMap entrySet                  newMap put entry getValue    entry getKey                       return new TreeMap lt String  String gt  newMap             return new TreeMap lt String  String gt  passedMap

User · Answer

Assuming Java  you could sort hashmap just like this   public LinkedHashMap lt Integer  String gt  sortHashMapByValues          HashMap lt Integer  String gt  passedMap        List lt Integer gt  mapKeys   new ArrayList lt  gt  passedMap keySet         List lt String gt  mapValues   new ArrayList lt  gt  passedMap values         Collections sort mapValues       Collections sort mapKeys        LinkedHashMap lt Integer  String gt  sortedMap           new LinkedHashMap lt  gt          Iterator lt String gt  valueIt   mapValues iterator        while  valueIt hasNext              String val   valueIt next            Iterator lt Integer gt  keyIt   mapKeys iterator             while  keyIt hasNext                  Integer key   keyIt next                String comp1   passedMap get key               String comp2   val               if  comp1 equals comp2                     keyIt remove                    sortedMap put key  val                   break                                    return sortedMap      Just a kick-off example  This way is more useful as it sorts the HashMap and keeps the duplicate values as well

User · Answer

package SortedSet   import java util     public class HashMapValueSort   public static void main String   args       final Map lt Integer  String gt  map   new HashMap lt Integer String gt         map put 4  Mango        map put 3  Apple        map put 5  Orange        map put 8  Fruits        map put 23  Vegetables        map put 1  Zebra        map put 5  Yellow        System out println map       final HashMapValueSort sort   new HashMapValueSort        final Set lt Map Entry lt Integer  String gt  gt  entry   map entrySet        final Comparator lt Map Entry lt Integer  String gt  gt  comparator   new Comparator lt Map Entry lt Integer  String gt  gt               Override         public int compare Map Entry lt Integer  String gt  o1  Map Entry lt Integer  String gt  o2                String value1   o1 getValue                String value2   o2 getValue                return value1 compareTo value2                        final SortedSet lt Map Entry lt Integer  String gt  gt  sortedSet   new TreeSet comparator       sortedSet addAll entry       final Map lt Integer String gt  sortedMap    new LinkedHashMap lt Integer  String gt         for Map Entry lt Integer  String gt  entry1   sortedSet            sortedMap put entry1 getKey   entry1 getValue               System out println sortedMap

User · Answer

As a kind of simple solution you can use temp TreeMap if you need just a final result   TreeMap lt String  Integer gt  sortedMap   new TreeMap lt String  Integer gt     for  Map Entry entry   map entrySet          sortedMap put  String  entry getValue     Integer entry getKey         This will get you strings sorted as keys of sortedMap

User · Answer

You don t  basically  A HashMap is fundamentally unordered  Any patterns you might see in the ordering should not be relied on   There are sorted maps such as TreeMap  but they traditionally sort by key rather than value  It s relatively unusual to sort by value - especially as multiple keys can have the same value   Can you give more context for what you re trying to do  If you re really only storing numbers  as strings  for the keys  perhaps a SortedSet such as TreeSet would work for you   Alternatively  you could store two separate collections encapsulated in a single class to update both at the same time

User · Answer

Try below code it works fine for me  You can choose both Ascending as well as descending order   import java util Collections  import java util Comparator  import java util HashMap  import java util LinkedHashMap  import java util LinkedList  import java util List  import java util Map  import java util Map Entry   public class SortMapByValue       public static boolean ASC   true      public static boolean DESC   false       public static void main String   args                    Creating dummy unsorted map         Map lt String  Integer gt  unsortMap   new HashMap lt String  Integer gt             unsortMap put  B   55           unsortMap put  A   80           unsortMap put  D   20           unsortMap put  C   70            System out println  Before sorting                  printMap unsortMap            System out println  After sorting ascending order                  Map lt String  Integer gt  sortedMapAsc   sortByComparator unsortMap  ASC           printMap sortedMapAsc             System out println  After sorting descindeng order                  Map lt String  Integer gt  sortedMapDesc   sortByComparator unsortMap  DESC           printMap sortedMapDesc               private static Map lt String  Integer gt  sortByComparator Map lt String  Integer gt  unsortMap  final boolean order                 List lt Entry lt String  Integer gt  gt  list   new LinkedList lt Entry lt String  Integer gt  gt  unsortMap entrySet                 Sorting the list based on values         Collections sort list  new Comparator lt Entry lt String  Integer gt  gt                          public int compare Entry lt String  Integer gt  o1                      Entry lt String  Integer gt  o2                                if  order                                        return o1 getValue   compareTo o2 getValue                                       else                                       return o2 getValue   compareTo o1 getValue                                                              Maintaining insertion order with the help of LinkedList         Map lt String  Integer gt  sortedMap   new LinkedHashMap lt String  Integer gt             for  Entry lt String  Integer gt  entry   list                        sortedMap put entry getKey    entry getValue                        return sortedMap             public static void printMap Map lt String  Integer gt  map                for  Entry lt String  Integer gt  entry   map entrySet                          System out println  Key       entry getKey       Value      entry getValue                         Edit  Version 2      Used new java feature like stream for-each etc      Map will be sorted by keys if values are same    import java util     import java util Map Entry   import java util stream Collectors    public class SortMapByValue         private static boolean ASC   true      private static boolean DESC   false      public static void main String   args                    Creating dummy unsorted map         Map lt String  Integer gt  unsortMap   new HashMap lt  gt             unsortMap put  B   55           unsortMap put  A   20           unsortMap put  D   20           unsortMap put  C   70            System out println  Before sorting                  printMap unsortMap            System out println  After sorting ascending order                  Map lt String  Integer gt  sortedMapAsc   sortByValue unsortMap  ASC           printMap sortedMapAsc             System out println  After sorting descending order                  Map lt String  Integer gt  sortedMapDesc   sortByValue unsortMap  DESC           printMap sortedMapDesc              private static Map lt String  Integer gt  sortByValue Map lt String  Integer gt  unsortMap  final boolean order                List lt Entry lt String  Integer gt  gt  list   new LinkedList lt  gt  unsortMap entrySet                 Sorting the list based on values         list sort  o1  o2  - gt  order   o1 getValue   compareTo o2 getValue       0                   o1 getKey   compareTo o2 getKey                      o1 getValue   compareTo o2 getValue      o2 getValue   compareTo o1 getValue       0                   o2 getKey   compareTo o1 getKey                      o2 getValue   compareTo o1 getValue              return list stream   collect Collectors toMap Entry  getKey  Entry  getValue   a  b  - gt  b  LinkedHashMap  new                private static void printMap Map lt String  Integer gt  map                map forEach  key  value  - gt  System out println  Key       key     Value       value

User · Answer

import java util ArrayList  import java util Collections  import java util HashMap  import java util List  import java util Map Entry   public class CollectionsSort                    param args         enter code here      public static void main String   args               TODO Auto-generated method stub          CollectionsSort colleciotns   new CollectionsSort             List lt combine gt  list   new ArrayList lt combine gt             HashMap lt String  Integer gt  h   new HashMap lt String  Integer gt             h put  nayanana   10           h put  lohith   5            for  Entry lt String  Integer gt  value   h entrySet                  combine a   colleciotns new combine value getValue                        value getKey                 list add a                      Collections sort list           for  int i   0  i  lt  list size    i                  System out println list get i                         public class combine implements Comparable lt combine gt             public int value          public String key           public combine int value  String key                this value   value              this key   key                      Override         public int compareTo combine arg0                   TODO Auto-generated method stub             return this value  gt  arg0 value   1   this value  lt  arg0 value   -1                       0                     public String toString                 return this value         this key

User · Answer

map entrySet   stream                    sorted  k1  k2  - gt  -k1 getValue   compareTo k2 getValue                      forEach k - gt  System out println k getKey            k getValue

[java] Sorting HashMap by values

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