How print out the contents of a HashMap String String in ascending order based on its values

Question

I have this HashMap that I need to print out in ascending order according to the values contained in it  not the keys     But the order when I print it out is seemingly random    What s the best way to print it out in ascending value order   Map lt String  String gt  codes   new HashMap lt String  String gt      codes put  A1    Aania    codes put  X1    Abatha    codes put  C1    Acathan    codes put  S1    Adreenas      In other words  the example above should print out as this   A1  Aania X1  Abatha C1  Acathan S1  Adreenas

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Create a TreeMap lt String String gt  Add each of the HashMap entries with the value as the key  iterate the TreeMap   If the values are nonunique  you would need a list in the second position

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you just need to use     Map lt  gt  toString   replace       n      and replaces the ending square bracket of each key value set with a new line

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the for loop of for Map Entry entry  codes entrySet    didn t work for me  Used Iterator instead    Iterator lt Map Entry lt String  String gt  gt  i   codes entrySet   iterator     while i hasNext         String key   i next   getKey        System out println key      codes get key

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It s time to add some lambdas   codes entrySet        stream        sorted Comparator comparing Map Entry  getValue        forEach System out  println

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You can use a list of the entry set rather than the key set and it is a more natural choice given you are sorting based on the value  This avoids a lot of unneeded lookups in the sorting and printing of the entries   Map lt String  String gt  map       List lt Map Entry lt String  String gt  gt  listOfEntries   new ArrayList lt Map Entry lt String  String gt  gt  map entrySet     Collections sort listOfEntries  new SortByValueComparator     for Map Entry lt String  String gt  entry  listOfEntries     System out println entry    static class SortByValueComparator implements Comparator lt Map Entry lt String  String gt  gt       public int compareTo Map Entry lt String  String gt  e1  Map Entry lt String  String gt  e2           return e1 getValue   compateTo e2 getValue

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SmartPhone   sp new SmartPhone 4    sp 0  new SmartPhone 1  HTC   desire   black  20000 10 true true    sp 1  new SmartPhone 2  samsung   grand   black  5000 10 false true    sp 2  new SmartPhone 14  google nexus   desire   black  2000 30 true false    sp 3  new SmartPhone 13  HTC   desire   white  50000 40 false false

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while  itr hasNext          Vehicle vc  Vehicle  itr next        if vc getVehicleType   equalsIgnoreCase s             count

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You ll need to make a list of the keys  sort them according to the corresponding values  then iterate over the sorted keys   Map lt String  String gt  map   getMyMap    List lt String gt  keys   new ArrayList lt String gt  map keySet     Collections sort keys  someComparator   for  String key  keys        System out println key          map get key        As for what to use for someComparator  here are some handy  generic Comparator-creating routines I often find useful   The first one sorts by the values according to their natural ordering  and the second allows you to specify any arbitrary Comparator to sort the values   public static  lt K  V extends Comparable lt   super V gt  gt          Comparator lt K gt  mapValueComparator final Map lt K  V gt  map        return new Comparator lt K gt              public int compare K key1  K key2                return map get key1  compareTo map get key2                        public static  lt K  V gt          Comparator lt K gt  mapValueComparator final Map lt K  V gt  map                                           final Comparator lt V gt  comparator        return new Comparator lt K gt              public int compare K key1  K key2                return comparator compare map get key1   map get key2

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the simplest and shortest code i think is this   public void listPrinter LinkedHashMap lt String  String gt  caseList         for Entry entry caseList entrySet              System out println  K   t  entry getKey      V   t  entry getValue

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Java 8  map entrySet   stream   sorted Map Entry comparingByValue    forEach System out  println

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Try   try       int cnt  m getSmartPhoneCount  HTC  true             System out println  total count of HTC   cnt       catch  NoSuchBrandSmartPhoneAvailableException e           TODO Auto-generated catch      e printStackTrace

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You aren t going to be able to do this from the HashMap class alone    I would take the Map lt String  String gt  codes  construct a reverse map of TreeMap lt String  String gt  reversedMap where you map the values of the codes Map to the keys  this would require your original Map to have a one-to-one mapping from key-to-value   Since the TreeMap provides Iterators which returns entries in ascending key order  this will give you the value key combination of the first map in the order  sorted by values  you desire   Map lt String  String gt  reversedMap   new TreeMap lt String  String gt  codes      then you just access the reversedMap however you like    for  Map Entry entry   reversedMap entrySet          System out println entry getKey            entry getValue         There are several collections libraries  commons-collections  Google Collections  etc  which have similar bidirectional Map implementations

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The simplest solution would be to use a sorted map like TreeMap instead of HashMap   If you do not have control over the map construction  then the minimal solution would be to construct a sorted set of keys  You don t really need a new map   Set lt String gt  sortedKeys   new TreeSet lt String gt     sortedKeys addAll codes keySet      for String key  sortedKeys       println key          codes get key

[java] How print out the contents of a HashMap<String, String> in ascending order based on its values?

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