RootCauseFinder improvements

core-java/src/main/java/com/baeldung/exceptions/RootCauseFinder.java

@@ -10,10 +10,13 @@ import java.util.Objects;
  */
 public class RootCauseFinder {
 
+    private RootCauseFinder() {
+    }
+
     public static Throwable findCauseUsingPlainJava(Throwable throwable) {
         Objects.requireNonNull(throwable);
         Throwable rootCause = throwable;
-        while (rootCause.getCause() != null) {
+        while (rootCause.getCause() != null && rootCause.getCause() != rootCause) {
             rootCause = rootCause.getCause();
         }
         return rootCause;

core-java/src/test/java/com/baeldung/exceptions/RootCauseFinderTest.java

@@ -75,6 +75,15 @@ public class RootCauseFinderTest {
         }
     }
 
+    @Test
+    public void givenNullDate_whenFindingRootCauseUsingApacheCommons_thenRootCauseNotFound() {
+        try {
+            AgeCalculator.calculateAge(null);
+        } catch (Exception ex) {
+            assertTrue(ExceptionUtils.getRootCause(ex) instanceof IllegalArgumentException);
+        }
+    }
+
     @Test
     public void givenWrongFormatDate_whenFindingRootCauseUsingGuava_thenRootCauseFound() {
         try {
@@ -93,4 +102,13 @@ public class RootCauseFinderTest {
         }
     }
 
+    @Test
+    public void givenNullDate_whenFindingRootCauseUsingGuava_thenRootCauseFound() {
+        try {
+            AgeCalculator.calculateAge(null);
+        } catch (Exception ex) {
+            assertTrue(Throwables.getRootCause(ex) instanceof IllegalArgumentException);
+        }
+    }
+
 }