Use Objects.requireNonNull().
MODIFY
src/main/java/org/apache/commons/io/FilenameUtils.java
src/main/java/org/apache/commons/io/FilenameUtils.java
import java.util.Collection;
import java.util.Deque;
import java.util.List;
+import java.util.Objects;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
@@ -537,11 +538,7 @@ public static String concat(final String basePath, final String fullFileNameToAd
*/
public static boolean directoryContains(final String canonicalParent, final String canonicalChild)
throws IOException {
-
- // Fail fast against NullPointerException
- if (canonicalParent == null) {
- throw new IllegalArgumentException("Directory must not be null");
- }
+ Objects.requireNonNull(canonicalParent, "canonicalParent");
if (canonicalChild == null) {
return false;

Use Objects.requireNonNull().