Monday, February 20, 2017

Java 8 stream - GroupingBy sum BigDecimal

Java 8 stream - GroupingBy and summing a BigDecimal field

 import java.math.BigDecimal;  
 import java.util.Arrays;  
 import java.util.List;  
 import java.util.Map;  
 import java.util.stream.Collectors;  
 public class C1 {  
      public static void main(String[] arg){  
           Map<String, BigDecimal> result = data().stream()
               .collect(Collectors.groupingBy(Emp::getDept, 
                        Collectors.mapping(Emp::getSalary, Collectors.reducing(BigDecimal.ZERO, BigDecimal::add))));  
           System.out.println(result);  
      }  
      static class Emp{  
           public Emp(String name, String dept, BigDecimal salary) {  
                super();  
                this.name = name;  
                this.dept = dept;  
                this.salary = salary;  
           }  
           private String name;  
           private String dept;  
           private BigDecimal salary;  
           public String getName() {  
                return name;  
           }  
           public String getDept() {  
                return dept;  
           }  
           public BigDecimal getSalary() {  
                return salary;  
           }  
      }  
      private static List<Emp> data(){  
           Emp e1 = new Emp("e1", "dept1", BigDecimal.valueOf(1.1));  
           Emp e2 = new Emp("e2", "dept1", BigDecimal.valueOf(1.1));  
           Emp e3 = new Emp("e3", "dept2", BigDecimal.valueOf(2.1));  
           Emp e4 = new Emp("e4", "dept2", BigDecimal.valueOf(1.9));  
           return Arrays.asList(e1, e2, e3, e4);  
      }  
 }  

1 comment:

Chinmayee Patra said...

Thanks a lot for explaining this example.
I was searching everywhere for this answer.