BAEL-1534: Detect the OS from Java (#3636)

* BAEL-1534: Mini-article completed.

* BAEL-1534: Changes incorporated.

* BAEL-1534: Changes incorporated.

* BAEL-1534: Changes incorporated.

* BAEL-1534: Changes incorporated.

core-java/src/main/java/com/baeldung/system/DetectOS.java

@@ -0,0 +1,18 @@
+package com.baeldung.system;
+
+import org.apache.commons.lang3.SystemUtils;
+
+public class DetectOS {
+
+    public String getOperatingSystem() {
+        String os = System.getProperty("os.name");
+        System.out.println("Using System Property: " + os);
+        return os;
+    }
+
+    public String getOperatingSystemSystemUtils() {
+        String os = SystemUtils.OS_NAME;
+        System.out.println("Using SystemUtils: " + os);
+        return os;
+    }
+}

core-java/src/test/java/com/baeldung/system/WhenDetectingOSTest.java

@@ -0,0 +1,25 @@
+package com.baeldung.system;
+
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+@Ignore
+public class WhenDetectingOSTest {
+
+    private DetectOS os = new DetectOS();
+
+    @Test
+    public void whenUsingSystemProperty_shouldReturnOS() {
+        String expected = "Windows 10";
+        String actual = os.getOperatingSystem();
+        Assert.assertEquals(expected, actual);
+    }
+
+    @Test
+    public void whenUsingSystemUtils_shouldReturnOS() {
+        String expected = "Windows 10";
+        String actual = os.getOperatingSystemSystemUtils();
+        Assert.assertEquals(expected, actual);
+    }
+}