diff --git a/java-streams/src/main/java/com/baeldung/stream/sum/. .. b/java-streams/src/main/java/com/baeldung/stream/sum/. ..
new file mode 100644
index 0000000000..8b13789179
--- /dev/null
+++ b/java-streams/src/main/java/com/baeldung/stream/sum/. ..	
@@ -0,0 +1 @@
+
diff --git a/java-streams/src/main/java/com/baeldung/stream/sum/ArithmeticUtils.java b/java-streams/src/main/java/com/baeldung/stream/sum/ArithmeticUtils.java
new file mode 100644
index 0000000000..3170b1fb31
--- /dev/null
+++ b/java-streams/src/main/java/com/baeldung/stream/sum/ArithmeticUtils.java
@@ -0,0 +1,8 @@
+package com.baeldung.stream.sum;
+
+public class ArithmeticUtils {
+
+    public static int add(int a, int b) {
+        return a + b;
+    }
+}
diff --git a/java-streams/src/main/java/com/baeldung/stream/sum/Item.java b/java-streams/src/main/java/com/baeldung/stream/sum/Item.java
new file mode 100644
index 0000000000..2f162d6eda
--- /dev/null
+++ b/java-streams/src/main/java/com/baeldung/stream/sum/Item.java
@@ -0,0 +1,31 @@
+package com.baeldung.stream.sum;
+
+public class Item {
+
+    private int id;
+    private Integer price;
+
+    public Item(int id, Integer price) {
+        super();
+        this.id = id;
+        this.price = price;
+    }
+
+    // Standard getters and setters
+    public long getId() {
+        return id;
+    }
+
+    public void setId(int id) {
+        this.id = id;
+    }
+
+    public Integer getPrice() {
+        return price;
+    }
+
+    public void setPrice(Integer price) {
+        this.price = price;
+    }
+
+}
diff --git a/java-streams/src/main/java/com/baeldung/stream/sum/StreamSumCalculator.java b/java-streams/src/main/java/com/baeldung/stream/sum/StreamSumCalculator.java
new file mode 100644
index 0000000000..2f63cf8629
--- /dev/null
+++ b/java-streams/src/main/java/com/baeldung/stream/sum/StreamSumCalculator.java
@@ -0,0 +1,59 @@
+package com.baeldung.stream.sum;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+public class StreamSumCalculator {
+
+    public static Integer getSumUsingCustomizedAccumulator(List<Integer> integers) {
+        return integers.stream()
+            .reduce(0, ArithmeticUtils::add);
+
+    }
+
+    public static Integer getSumUsingJavaAccumulator(List<Integer> integers) {
+        return integers.stream()
+            .reduce(0, Integer::sum);
+
+    }
+
+    public static Integer getSumUsingReduce(List<Integer> integers) {
+        return integers.stream()
+            .reduce(0, (a, b) -> a + b);
+
+    }
+
+    public static Integer getSumUsingCollect(List<Integer> integers) {
+
+        return integers.stream()
+            .collect(Collectors.summingInt(Integer::intValue));
+
+    }
+
+    public static Integer getSumUsingSum(List<Integer> integers) {
+
+        return integers.stream()
+            .mapToInt(Integer::intValue)
+            .sum();
+    }
+
+    public static Integer getSumOfMapValues(Map<Object, Integer> map) {
+
+        return map.values()
+            .stream()
+            .mapToInt(Integer::valueOf)
+            .sum();
+    }
+
+    public static Integer getSumIntegersFromString(String str) {
+
+        Integer sum = Arrays.stream(str.split(" "))
+            .filter((s) -> s.matches("\\d+"))
+            .mapToInt(Integer::valueOf)
+            .sum();
+
+        return sum;
+    }
+}
diff --git a/java-streams/src/main/java/com/baeldung/stream/sum/StreamSumCalculatorWithObject.java b/java-streams/src/main/java/com/baeldung/stream/sum/StreamSumCalculatorWithObject.java
new file mode 100644
index 0000000000..b83616928e
--- /dev/null
+++ b/java-streams/src/main/java/com/baeldung/stream/sum/StreamSumCalculatorWithObject.java
@@ -0,0 +1,38 @@
+package com.baeldung.stream.sum;
+
+import java.util.List;
+import java.util.stream.Collectors;
+
+public class StreamSumCalculatorWithObject {
+
+    public static Integer getSumUsingCustomizedAccumulator(List<Item> items) {
+        return items.stream()
+            .map(x -> x.getPrice())
+            .reduce(0, ArithmeticUtils::add);
+    }
+
+    public static Integer getSumUsingJavaAccumulator(List<Item> items) {
+        return items.stream()
+            .map(x -> x.getPrice())
+            .reduce(0, Integer::sum);
+    }
+
+    public static Integer getSumUsingReduce(List<Item> items) {
+        return items.stream()
+            .map(item -> item.getPrice())
+            .reduce(0, (a, b) -> a + b);
+    }
+
+    public static Integer getSumUsingCollect(List<Item> items) {
+        return items.stream()
+            .map(x -> x.getPrice())
+            .collect(Collectors.summingInt(Integer::intValue));
+    }
+
+    public static Integer getSumUsingSum(List<Item> items) {
+        return items.stream()
+            .mapToInt(x -> x.getPrice())
+            .sum();
+    }
+
+}
diff --git a/java-streams/src/test/java/com/baeldung/stream/sum/. .. b/java-streams/src/test/java/com/baeldung/stream/sum/. ..
new file mode 100644
index 0000000000..8b13789179
--- /dev/null
+++ b/java-streams/src/test/java/com/baeldung/stream/sum/. ..	
@@ -0,0 +1 @@
+
diff --git a/java-streams/src/test/java/com/baeldung/stream/sum/StreamSumUnitTest.java b/java-streams/src/test/java/com/baeldung/stream/sum/StreamSumUnitTest.java
new file mode 100644
index 0000000000..46e1af9a4a
--- /dev/null
+++ b/java-streams/src/test/java/com/baeldung/stream/sum/StreamSumUnitTest.java
@@ -0,0 +1,136 @@
+package com.baeldung.stream.sum;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.junit.jupiter.api.Test;
+
+public class StreamSumUnitTest {
+
+    @Test
+    public void givenListOfIntegersWhenSummingUsingCustomizedAccumulatorThenCorrectValueReturned() {
+        List<Integer> integers = Arrays.asList(1, 2, 3, 4, 5);
+        Integer sum = StreamSumCalculator.getSumUsingCustomizedAccumulator(integers);
+        assertEquals(15, sum.intValue());
+
+    }
+
+    @Test
+    public void givenListOfIntegersWhenSummingUsingJavaAccumulatorThenCorrectValueReturned() {
+        List<Integer> integers = Arrays.asList(1, 2, 3, 4, 5);
+        Integer sum = StreamSumCalculator.getSumUsingJavaAccumulator(integers);
+        assertEquals(15, sum.intValue());
+    }
+
+    @Test
+    public void givenListOfIntegersWhenSummingUsingReduceThenCorrectValueReturned() {
+        List<Integer> integers = Arrays.asList(1, 2, 3, 4, 5);
+        Integer sum = StreamSumCalculator.getSumUsingReduce(integers);
+        assertEquals(15, sum.intValue());
+    }
+
+    @Test
+    public void givenListOfIntegersWhenSummingUsingCollectThenCorrectValueReturned() {
+        List<Integer> integers = Arrays.asList(1, 2, 3, 4, 5);
+        Integer sum = StreamSumCalculator.getSumUsingCollect(integers);
+        assertEquals(15, sum.intValue());
+    }
+
+    @Test
+    public void givenListOfIntegersWhenSummingUsingSumThenCorrectValueReturned() {
+        List<Integer> integers = Arrays.asList(1, 2, 3, 4, 5);
+        Integer sum = StreamSumCalculator.getSumUsingSum(integers);
+        assertEquals(15, sum.intValue());
+    }
+
+    @Test
+    public void givenListOfItemsWhenSummingUsingCustomizedAccumulatorThenCorrectValueReturned() {
+        Item item1 = new Item(1, 10);
+        Item item2 = new Item(2, 15);
+        Item item3 = new Item(3, 25);
+        Item item4 = new Item(4, 40);
+
+        List<Item> items = Arrays.asList(item1, item2, item3, item4);
+
+        Integer sum = StreamSumCalculatorWithObject.getSumUsingCustomizedAccumulator(items);
+        assertEquals(90, sum.intValue());
+
+    }
+
+    @Test
+    public void givenListOfItemsWhenSummingUsingJavaAccumulatorThenCorrectValueReturned() {
+        Item item1 = new Item(1, 10);
+        Item item2 = new Item(2, 15);
+        Item item3 = new Item(3, 25);
+        Item item4 = new Item(4, 40);
+
+        List<Item> items = Arrays.asList(item1, item2, item3, item4);
+
+        Integer sum = StreamSumCalculatorWithObject.getSumUsingJavaAccumulator(items);
+        assertEquals(90, sum.intValue());
+    }
+
+    @Test
+    public void givenListOfItemsWhenSummingUsingReduceThenCorrectValueReturned() {
+        Item item1 = new Item(1, 10);
+        Item item2 = new Item(2, 15);
+        Item item3 = new Item(3, 25);
+        Item item4 = new Item(4, 40);
+
+        List<Item> items = Arrays.asList(item1, item2, item3, item4);
+
+        Integer sum = StreamSumCalculatorWithObject.getSumUsingReduce(items);
+        assertEquals(90, sum.intValue());
+    }
+
+    @Test
+    public void givenListOfItemsWhenSummingUsingCollectThenCorrectValueReturned() {
+        Item item1 = new Item(1, 10);
+        Item item2 = new Item(2, 15);
+        Item item3 = new Item(3, 25);
+        Item item4 = new Item(4, 40);
+
+        List<Item> items = Arrays.asList(item1, item2, item3, item4);
+
+        Integer sum = StreamSumCalculatorWithObject.getSumUsingCollect(items);
+        assertEquals(90, sum.intValue());
+    }
+
+    @Test
+    public void givenListOfItemsWhenSummingUsingSumThenCorrectValueReturned() {
+        Item item1 = new Item(1, 10);
+        Item item2 = new Item(2, 15);
+        Item item3 = new Item(3, 25);
+        Item item4 = new Item(4, 40);
+
+        List<Item> items = Arrays.asList(item1, item2, item3, item4);
+
+        Integer sum = StreamSumCalculatorWithObject.getSumUsingSum(items);
+        assertEquals(90, sum.intValue());
+    }
+
+    @Test
+    public void givenMapWhenSummingThenCorrectValueReturned() {
+        Map<Object, Integer> map = new HashMap<Object, Integer>();
+        map.put(1, 10);
+        map.put(2, 15);
+        map.put(3, 25);
+        map.put(4, 40);
+
+        Integer sum = StreamSumCalculator.getSumOfMapValues(map);
+        assertEquals(90, sum.intValue());
+    }
+
+    @Test
+    public void givenStringWhenSummingThenCorrectValueReturned() {
+        String string = "Item1 10 Item2 25 Item3 30 Item4 45";
+
+        Integer sum = StreamSumCalculator.getSumIntegersFromString(string);
+        assertEquals(110, sum.intValue());
+    }
+
+}