change method to return Optionals (eugenp#4464)

rajat-garg · pauljervis · commit 974637a27372 · 2018-06-17T20:41:40.000+01:00
* change method to return Optionals

* add check for empty Optional
diff --git a/core-java/src/main/java/com/baeldung/extension/Extension.java b/core-java/src/main/java/com/baeldung/extension/Extension.java
@@ -3,18 +3,18 @@
 import com.google.common.io.Files;
 import org.apache.commons.io.FilenameUtils;
 
+import java.util.Optional;
+
 public class Extension {
     //Instead of file name we can also specify full path of a file eg. /baeldung/com/demo/abc.java
     public String getExtensionByApacheCommonLib(String filename) {
         return FilenameUtils.getExtension(filename);
     }
 
-    public String getExtensionByStringHandling(String filename) {
-        String fileExtension = "";
-        if (filename.contains(".") && filename.lastIndexOf(".") != 0) {
-            fileExtension = filename.substring(filename.lastIndexOf(".") + 1);
-        }
-        return fileExtension;
+    public Optional<String> getExtensionByStringHandling(String filename) {
+        return Optional.ofNullable(filename)
+                       .filter(f -> f.contains("."))
+                      .map(f -> f.substring(filename.lastIndexOf(".") + 1));
     }
 
     public String getExtensionByGuava(String filename) {
diff --git a/core-java/src/test/java/com/baeldung/extension/ExtensionUnitTest.java b/core-java/src/test/java/com/baeldung/extension/ExtensionUnitTest.java
@@ -3,6 +3,8 @@
 import org.junit.Assert;
 import org.junit.Test;
 
+import java.util.Optional;
+
 public class ExtensionUnitTest {
     private Extension extension = new Extension();
 
@@ -16,8 +18,9 @@ public void getExtension_whenApacheCommonIO_thenExtensionIsTrue() {
     @Test
     public void getExtension_whenStringHandle_thenExtensionIsTrue() {
         String expectedExtension = "java";
-        String actualExtension = extension.getExtensionByStringHandling("Demo.java");
-        Assert.assertEquals(expectedExtension, actualExtension);
+        Optional<String> actualExtension = extension.getExtensionByStringHandling("Demo.java");
+        Assert.assertTrue(actualExtension.isPresent());
+        actualExtension.ifPresent(ext -> Assert.assertEquals(expectedExtension,ext));
     }
 
     @Test
