Java-8: How to sort Map (based on values) using Map.Entry#comparingByValue while ignoring case sensitivity?

Question

I want to sort a Map based on values alphabetically and ignoring case sensitivity and return the list of Keys.

 /**
   * This method will sort allCostPlanDetailsRows based on Value in <Key,Value> pair
   *
   * @param sortingOrder_ whether to sort the LinkedHashMap in Ascending order or Descending order
   * @return List<String> returns List of costPlanDetailsRowId in sorted order
   */
  private List<String> sortCostPlanDetailRows( SortingOrder sortingOrder_ )
  {
    return _allCostPlanDetailRows
      .entrySet()
      .stream()
      .sorted( sortingOrder_ == SortingOrder.DESC ? Map.Entry.<String, String>comparingByValue(Comparator.nullsFirst(Comparator.naturalOrder())).reversed() : Map.Entry.comparingByValue(Comparator.nullsFirst(
          Comparator.naturalOrder())) )
      .map( Map.Entry::getKey )
      .collect( Collectors.toList() );
  }

How can I achieve this?

Note: Suggestions are welcomed on if I can improve above piece of code.

Mureinik · Accepted Answer · 2017-05-29 06:44:49Z

8

Instead of using the naturalOrder comparator, you can use String.CASE_INSENSITIVE_ORDER:

return _allCostPlanDetailRows
      .entrySet()
      .stream()
      .sorted( sortingOrder_ == SortingOrder.DESC ? Map.Entry.<String, String>comparingByValue(Comparator.nullsFirst(String.CASE_INSENSITIVE_ORDER)).reversed() : Map.Entry.comparingByValue(Comparator.nullsFirst(
          String.CASE_INSENSITIVE_ORDER)) )
      .map( Map.Entry::getKey )
      .collect( Collectors.toList() );

answered May 29, 2017 at 6:44

Mureinik

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2 Comments

Neeraj Jain Over a year ago

thanks just one doubt, Will that be applicable for only Null values or for all other values as well?

Mureinik Over a year ago

You will have the nulls first, as you're using Comparator.nullsFirst. All the strings that aren't nulls will then be sorted regardless of their case.

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