README.md

OrderedMapUtils

Provide utils to work on consecutive elements in an ordered map (LinkedHashMap or SortedMap).

It uses the StreamsUtils API

Let's imagine you have a LinkedHashMap of temperature records.

• key is the day of the year
• value is the average temperature of the day
  Data come from the meteorological station in Trappes (France)

LinkedHashMap<Date, Float> temperatures = new LinkedHashMap<Date, Float>();  
SimpleDateFormat formatter = new SimpleDateFormat("dd/MM/yyyy");  
try {  
  temperatures.put(formatter.parse("01/01/2016"), 8.9f);  
  temperatures.put(formatter.parse("02/01/2016"), 10f);  
  ...  
  temperatures.put(formatter.parse("31/12/2016"), -3.2f);  
} catch (ParseException e) {  
  e.printStackTrace();  
}  

With the class OrderedMapUtils and two provided classes,

• KeyPair that handles a key and its successive in the map
• Operation<K,R> that handles a key, its successive in the map and the result of an operation applied to the two values in the map you can easily work on consecutive elements to:

Apply an operation

Difference of temperature from one day to the next day:

OrderedMapUtils.apply(temperatures, (t1, t2) -> (t2 - t1)).values().stream()  
  .forEachOrdered(  
       e -> System.out.println("From " + e.getKey() + " To " + e.getNextKey() + " : " + e.getResult())  
  );  

From Fri Jan 01 2016 To Sat Jan 02 2016 : 1.1
From Sat Jan 02 2016 To Sun Jan 03 2016 : -2.3
...
From Fri Dec 30 2016 To Sat Dec 31 2016 : -1.3

Filter all maximum of an operation

Maximum day-to-day thermal amplitude:

OrderedMapUtils.filterAllMax(temperatures, (t1, t2) -> Math.abs(t2 - t1)).stream()  
  .forEachOrdered(  
       e -> System.out.println("From " + e.getKey() + " To " + e.getNextKey() + " : " + e.getResult())  
  );  

From Sat Apr 02 2016 To Sun Apr 03 2016 : 10.0

Filter all minimum of an operation

Minimum day-to-day thermal amplitude:

OrderedMapUtils.filterAllMin(temperatures, (t1, t2) -> Math.abs(t2 - t1)).stream()  
  .forEachOrdered(  
       e -> System.out.println("From " + e.getKey() + " To " + e.getNextKey() + " : " + e.getResult())  
  );  

From Sun Mar 27 2016 To Mon Mar 28 2016 : 0.0
From Wed Jun 29 2016 To Thu Jun 30 2016 : 0.0
From Wed Aug 24 2016 To Thu Aug 25 2016 : 0.0
From Fri Sep 02 2016 To Sat Sep 03 2016 : 0.0
From Wed Nov 30 2016 To Thu Dec 01 2016 : 0.0
From Tue Dec 06 2016 To Wed Dec 07 2016 : 0.0

Find the average of an operation

Average day-to-day thermal amplitude:

System.out.println("Average day-to-day thermal amplitude: " //
+ OrderedMapUtils.average(temperatures, (t1, t2) -> Math.abs(t2 - t1)));  

Average day-to-day thermal amplitude: 2.1

Test the result of an operation

Check if day-to-day thermal amplitude is greater than 8°:

OrderedMapUtils.test(temperatures, (t1, t2) -> Math.abs(t2 - t1) >= 8f).values().stream()  
  .forEachOrdered(  
       e -> System.out.println("From " + e.getKey() + " to " + e.getNextKey() + " : " + e.getResult())  
  );

From Fri Jan 01 2016 to Sat Jan 02 CET 2016 : false
From Sat Jan 02 2016 to Sun Jan 03 2016 : false
...
From Sat Apr 02 2016 to Sun Apr 03 2016 : true
...

Filter by a test

List periods where day-to-day thermal amplitude is greater than 8°:

OrderedMapUtils.filterTests(temperatures, (t1, t2) -> Math.abs(t2 - t1) >= 8f, true).stream()  
  .forEachOrdered(  
       e -> System.out.println("From " + e.getKey() + " to " + e.getNextKey())  
  );

From Sat Apr 02 2016 to Sun Apr 03 2016
From Fri May 13 2016 to Sat May 14 2016
From Sat May 21 2016 to Sun May 22 2016

Filter by a grouped of consecutive successful tests

List periods of exactly 5 consecutive days of temperature increase:

OrderedMapUtils.filterGroupedConsecutiveTests(temperatures, (t1, t2) -> t2 - t1 > 0f, true, 5, 5).stream()  
  .forEachOrdered(  
       e -> System.out.println("From " + e.get(0).getKey() + " to " + e.get(e.size() - 1).getNextKey())  
  );

From Mon Sep 19 2016 to Sat Sep 24 2016

Filter all maximum of a grouped of consecutive successful tests

List the longest periods of consecutive days of temperature increase:

OrderedMapUtils.filterAllMaxGroupedConsecutiveTests(temperatures, (t1, t2) -> t2 - t1 > 0f, true).stream()  
  .forEachOrdered(  
       e -> System.out.println("From " + e.get(0).getKey() + " to " + e.get(e.size() - 1).getNextKey())  
  );  

From Wed Jul 13 2016 to Tue Jul 19 2016
From Tue Dec 20 2016 to Mon Dec 26 2016

Find the average a grouped of consecutive successful tests

Average duration of consecutive days of temperature increase:

System.out.println("Average duration of consecutive days of temperature increase: " //
+ OrderedMapUtils.averageGroupedConsecutiveTests(temperatures, (t1, t2) -> t2 - t1 > 0f, true));  

Average duration of consecutive days of temperature increase: 1.8