In this tutorial, we will see “How to perform sum operation on arrays, list and map objects using reduce method in Java 8”.
Sum of integers in Java 8 - array, list and map using reduce method...!!! Share on X
Example
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.function.IntBinaryOperator;
public class SumOfArrayListMap_Reduce_Java8_Stream_Example {
public static void main(String[] args) {
sumOfArrayUsingReduce();
sumOfListUsingReduce();
sumOfMapUsingReduce();
}
private static void sumOfArrayUsingReduce() {
int[] arrayObj = {5,44,22,11,23,82,11,91};
int sumOfArray;
//Reduce Method 1
System.out.println("Array Sum: Reduce method with IntBinaryOperator");
IntBinaryOperator intBinaryOperator = (x, y) - > x + y;
sumOfArray = Arrays.stream(arrayObj).reduce(0, intBinaryOperator);
System.out.println(sumOfArray);
//Reduce Method 2
System.out.println("\nArray Sum: Reduce method with method reference");
sumOfArray = Arrays.stream(arrayObj).reduce(0, Integer::sum);
System.out.println(sumOfArray);
}
private static void sumOfListUsingReduce() {
List < Integer > listObj = Arrays.asList(5, 10, 33, 11, 55);
int sumOfList;
System.out.println("\nList Sum: Reduce method with BinaryOperator");
sumOfList = listObj.stream().reduce(0, (x, y) - > x + y);
System.out.println(sumOfList);
}
private static void sumOfMapUsingReduce() {
Map < Integer, Integer > mapObj = new HashMap < > ();
mapObj.put(1, 5);
mapObj.put(2, 10);
mapObj.put(3, 15);
mapObj.put(4, 20);
mapObj.put(5, 25);
int sumOfMap;
System.out.println("\nMap Sum: Reduce method with method reference");
sumOfMap = mapObj.values().stream().reduce(0, Integer::sum);
System.out.println(sumOfMap);
}
}
Output:
Array Sum: Reduce method with IntBinaryOperator 289 Array Sum: Reduce method with method reference 289 List Sum: Reduce method with BinaryOperator 114 Map Sum: Reduce method with method reference 75
Sum of integers in Java 8 - array, list and map using reduce method...!!! Share on X
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