Find number of elements in range from map object

  • A+

Map structure and data is given below

Map<String, BigDecimal> 

A, 12

B, 23

C, 67

D, 99

Now i want to group values in range, output has range as key and number of elements there as value. Like below:

0-25, 2

26-50, 0

51-75, 1

76-100, 1

How can we do this using java streams ?

You can do it like that:

public class MainClass {     public static void main(String[] args) {         Map<String, BigDecimal> aMap=new HashMap<>();          aMap.put("A",new BigDecimal(12));         aMap.put("B",new BigDecimal(23));         aMap.put("C",new BigDecimal(67));         aMap.put("D",new BigDecimal(99));          Map<String, Long> o =  aMap.entrySet().stream().collect(Collectors.groupingBy( a ->{              //Do the logic here to return the group by function              if(a.getValue().compareTo(new BigDecimal(0))>0 &&                      a.getValue().compareTo(new BigDecimal(25))<0)                  return "0-25";               if(a.getValue().compareTo(new BigDecimal(26))>0 &&                      a.getValue().compareTo(new BigDecimal(50))<0)                  return "26-50";               if(a.getValue().compareTo(new BigDecimal(51))>0 &&                      a.getValue().compareTo(new BigDecimal(75))<0)                  return "51-75";              if(a.getValue().compareTo(new BigDecimal(76))>0 &&                      a.getValue().compareTo(new BigDecimal(100))<0)                  return "76-100";               return "not-found";          }, Collectors.counting()));           System.out.print("Result="+o);       }  } 

Result is : Result={0-25=2, 76-100=1, 51-75=1}

I couldn't find a better way to do that check for big decimals but you can think about how to improve it :) Maybe make an external method that does that trick


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