Sorting hashmap based on keys

Question

I have the following hashmap in java       B046 0 0  A061 3 0  A071 0 0  B085 0 0  B075 3 0  B076 9 0  B086 3 0  B095 0 0  B096 0 0  A052 0 0  B066 0 0  B056 9 0  B065 0 0  B055 9 0    How should I go about sorting the hashmap such that the Alphabet  followed by the numerical figures are taken into account   The resulting hashmap should look like this       A052 0 0 A061 3 0 A071 0 0 B046 0 0 B055 9 0 B056 9 0 B065 0 0 B066 0 0 B075 3 0 B076 9 0 B085 0 0 B086 3 0 B095 0 0 B096 0 0    Appreciate the help

User · Accepted Answer

Use sorted TreeMap   Map lt String  Float gt  map   new TreeMap lt  gt  yourMap     It will automatically put entries sorted by keys  I think natural String ordering will be fine in your case   Note that HashMap due to lookup optimizations does not preserve order

User · Answer

Use a TreeMap  although having a map  look like that  is a bit nebulous--you could also just sort the keys based on your criteria and iterate over the map  retrieving each object

User · Answer

Using the TreeMap you can sort the Map   Map lt String  String gt  map   new HashMap lt String  String gt             Map lt String  String gt  treeMap   new TreeMap lt String  String gt  map     show hashmap after the sort for  String str   treeMap keySet          System out println str

User · Answer

TreeMap will automatically sort in ascending order  If you want to sort in descending order  use the following code   Copy the below code within your class and outside of the main execute method   static class DescOrder implements Comparator lt String gt         Override     public int compare String o1  String o2                  return o2 compareTo o1                 Then in your logic   TreeMap lt String  String gt  map   new TreeMap lt String  String gt  new DescOrder     map put  A    test1    map put  C    test3    map put  E    test5    map put  B    test2    map put  D    test4

User · Answer

Use TreeMap  Constructor    Map lt String  Float gt  sortedMap   new TreeMap lt  gt  yourMap     Use TreeMap  PutAll method    Map lt String  Float gt  sortedMap   new TreeMap lt  gt     sortedMap putAll yourMap     Implementation of Map interface    TreeMap - Automatically sort the keys in ascending order while inserting  HashMap - Order of insertion won t be maintained  LinkedHashMap - Order of insertion will be maintained

User · Answer

TreeMap is your best bet for these kind of sorting  Natural   TreeMap naturally sorts according to the keys   HashMap does not preserve insertion order nor does it sort the map  LinkedHashMap keeps the insertion order but doesn t sort the map automatically  Only TreeMap in the Map interface sorts the map according to natural order  Numerals first  upper-case alphabet second  lower-case alphabet last

User · Answer

You can use TreeMap which will store values in sorted form    Map  lt String  String gt  map   new TreeMap  lt String  String gt

User · Answer

Use a TreeMap with a custom comparator   class MyComparator implements Comparator lt String gt                public int compare String o1 String o2                           Your logic for comparing the key strings                  TreeMap lt String  Float gt  tm   new TreeMap lt String   Float gt  new MyComparator       As you add new elements  they will be automatically sorted   In your case  it might not even be necessary to implement a comparator because String ordering might be sufficient  But if you want to implement special cases  like lower case alphas appear before upper case  or treat the numbers a certain way  use the comparator

User · Answer

Just use a TreeMap  It implements the SortedMap interface  and thus automatically sorts the keys it contains  Your keys can just be sorted alphabetically to get the desired result  so you don t even need to provide a comparator   HashMaps are never sorted  The only thing you coulkd do with a HashMap is get all the keys  and store them in a sorted set or in a List and sort the List

[java] Sorting hashmap based on keys

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