BAEL-1330 Primitive Type Streams in Java 8 (#3106)

* initial commit for first article evaluation

* fixed compilation error

* removed final keywords for compliance

* added unit tests and refactored as needed

* refactored application-context.xml to use self-closing tags

* renamed tests to use UnitTest suffix

* removed unnecessary annotation

* added code samples for primitive streams

* removed sample code and tests for evaluation article

* renamed unit test to proper unit test naming

* added a test to show boxed method

* added the assertion to the test fox boxed

* changed mapToInt test to use Arrays.asList instead of a POJO as per Grzegorz and Eugen

core-java-8/src/main/java/com/baeldung/stream/PrimitiveStreams.java

@@ -0,0 +1,23 @@
+package com.baeldung.stream;
+
+import java.util.Arrays;
+import java.util.stream.IntStream;
+
+class PrimitiveStreams {
+
+    int min(int[] integers) {
+        return Arrays.stream(integers).min().getAsInt();
+    }
+
+    int max(int... integers) {
+        return IntStream.of(integers).max().getAsInt();
+    }
+
+    int sum(int... integers) {
+        return IntStream.of(integers).sum();
+    }
+
+    double avg(int... integers) {
+        return IntStream.of(integers).average().getAsDouble();
+    }
+}

core-java-8/src/test/java/com/baeldung/stream/PrimitiveStreamsUnitTest.java

@@ -0,0 +1,97 @@
+package com.baeldung.stream;
+
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+public class PrimitiveStreamsUnitTest {
+
+    private PrimitiveStreams streams = new PrimitiveStreams();
+
+    @Test
+    public void givenAnArrayOfIntegersWhenMinIsCalledThenCorrectMinIsReturned() {
+        int[] integers = new int[] {20, 98, 12, 7, 35};
+        int min = streams.min(integers); // returns 7
+
+        assertEquals(7, min);
+    }
+
+    @Test
+    public void givenAnArrayOfIntegersWhenMaxIsCalledThenCorrectMaxIsReturned() {
+        int max = streams.max(20, 98, 12, 7, 35);
+
+        assertEquals(98, max);
+    }
+
+    @Test
+    public void givenAnArrayOfIntegersWhenSumIsCalledThenCorrectSumIsReturned() {
+        int sum = streams.sum(20, 98, 12, 7, 35);
+
+        assertEquals(172, sum);
+    }
+
+    @Test
+    public void givenAnArrayOfIntegersWhenAvgIsCalledThenCorrectAvgIsReturned() {
+        double avg = streams.avg(20, 98, 12, 7, 35);
+
+        assertTrue(34.4 == avg);
+    }
+
+    @Test
+    public void givenARangeOfIntegersWhenIntStreamSumIsCalledThenCorrectSumIsReturned() {
+        int sum = IntStream.range(1, 10).sum();
+
+        assertEquals(45, sum);
+    }
+
+    @Test
+    public void givenARangeClosedOfIntegersWhenIntStreamSumIsCalledThenCorrectSumIsReturned() {
+        int sum = IntStream.rangeClosed(1, 10).sum();
+
+        assertEquals(55, sum);
+    }
+
+    @Test
+    public void givenARangeWhenForEachIsCalledThenTheIndicesWillBePrinted() {
+        IntStream.rangeClosed(1, 5).parallel().forEach(System.out::println);
+    }
+
+    @Test
+    public void givenAnArrayWhenSumIsCalledThenTheCorrectSumIsReturned() {
+
+        int sum = Arrays.asList(33,45).stream().mapToInt(a -> a).sum();
+
+        assertEquals(78, sum);
+    }
+
+    @Test
+    public void givenAnIntStreamThenGetTheEvenIntegers() {
+        List<Integer> evenInts = IntStream.rangeClosed(1, 10)
+          .filter(i -> i % 2 == 0)
+          .boxed()
+          .collect(Collectors.toList());
+
+        List<Integer> expected = IntStream.of(2, 4, 6, 8, 10).boxed().collect(Collectors.toList());
+
+        assertEquals(expected, evenInts);
+    }
+
+    class Person {
+        private int age;
+
+        Person(int age) {
+            this.age = age;
+        }
+
+        int getAge() {
+            return age;
+        }
+    }
+}