Adding new methods for calculating the sum (#6088)

* Creating new module

Creating new module for Hexagonal Architecture

* Adding Java classes

Adding Java classes used in the example

* Adding the pom.xml file

Adding the pom.xml file.

* Update the pom.xml file

Update the pom.xml file

* BAEL-2498: Creating new folder

Creating new folder for Java 8 sum with Streams examples

* BAEL-2498: Uploading java Classes

Adding the Java classes containing examples of different methods to calculate the sum using Java 8 Streams

* BAEL-2498: Creating new folder

Creating new folder for sum unit tests

* BAEL-2498: Adding the unit tests

Adding the unit tests for the methods that calculate the sum using the Java Streams

* Add files via Upload

- Adding a method for calculating the sum of a map´s values
- Adding a method for calculating the sum of numbers within a String object

* Add files via upload

- Adding a method for calculating the sum of a map´s values
- Adding a method for calculating the sum of numbers within a String object

* Delete . ...

* Delete pom.xml

* Delete User.java

* Delete UserControler.java

* Delete UserDataBaseAdapter.java

* Delete UserInterfaceAdapter.java

* Delete UserDataBasePort.java

* Delete UserInterfacePort.java

* Delete UserService.java

java-streams/src/main/java/com/baeldung/stream/sum/. ..

@@ -0,0 +1 @@
+

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;
+    }
+}

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;
+    }
+
+}

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;
+    }
+}

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();
+    }
+
+}