add NullMarked

Author: jamesward

src/main/java/org/webjars/WebJarCache.java

@@ -1,6 +1,8 @@
 package org.webjars;
 
 
+import org.jspecify.annotations.NullMarked;
+
 import java.util.Optional;
 import java.util.function.Function;
 
@@ -9,6 +11,7 @@
  * Since classpath resources are essentially immutable, the WebJarsCache does not have the concept of expiry.
  * Cache keys and values are Strings because that is all that is needed.
  */
+@NullMarked
 public interface WebJarCache {
 
     Optional<String> computeIfAbsent(String key, Function<String, Optional<String>> function);

src/main/java/org/webjars/WebJarCacheDefault.java

@@ -1,9 +1,13 @@
 package org.webjars;
 
+import org.jspecify.annotations.NullMarked;
+
 import java.util.Optional;
 import java.util.concurrent.ConcurrentMap;
 import java.util.function.Function;
 
+
+@NullMarked
 public class WebJarCacheDefault implements WebJarCache {
 
     final ConcurrentMap<String, Optional<String>> cache;

src/test/java/org/webjars/WebJarVersionLocatorTest.java

@@ -3,6 +3,7 @@
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNull;
 
+import org.jspecify.annotations.NullMarked;
 import org.junit.Test;
 
 import java.util.Optional;
@@ -46,6 +47,7 @@ public void full_path_exists_version_supplied() {
     public void cache_is_populated_on_lookup() {
         AtomicInteger numLookups = new AtomicInteger(0);
 
+        @NullMarked
         class InspectableCache implements WebJarCache {
             final ConcurrentHashMap<String, Optional<String>> cache = new ConcurrentHashMap<>();