Add a computeIfAbsent method to the Cache

daemon/src/main/java/org/mvndaemon/mvnd/cache/factory/Cache.java

@@ -16,6 +16,7 @@
 package org.mvndaemon.mvnd.cache.factory;
 
 import java.util.function.BiPredicate;
+import java.util.function.Function;
 
 /**
  * Cache containing records that can be invalidated.
@@ -53,4 +54,9 @@ public interface Cache<K, V extends CacheRecord> {
      */
     void removeIf(BiPredicate<K, V> predicate);
 
+    /**
+     * Get or compute the cached value if absent and return it.
+     */
+    V computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction);
+
 }

daemon/src/main/java/org/mvndaemon/mvnd/cache/factory/TimestampCacheFactory.java

@@ -26,6 +26,7 @@ import java.util.Objects;
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.function.BiPredicate;
+import java.util.function.Function;
 import java.util.stream.Collectors;
 import javax.inject.Named;
 import javax.inject.Singleton;
@@ -145,5 +146,12 @@ public class TimestampCacheFactory extends AbstractLogEnabled implements CacheFa
             }
         }
 
+        @Override
+        public V computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction) {
+            return map.computeIfAbsent(key, k -> {
+                V v = mappingFunction.apply(k);
+                return new Record<>(v);
+            }).record;
+        }
     }
 }

daemon/src/main/java/org/mvndaemon/mvnd/cache/factory/WatchServiceCacheFactory.java

@@ -29,6 +29,7 @@ import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.function.BiPredicate;
+import java.util.function.Function;
 import javax.inject.Named;
 import javax.inject.Singleton;
 import org.codehaus.plexus.logging.AbstractLogEnabled;
@@ -241,5 +242,14 @@ public class WatchServiceCacheFactory extends AbstractLogEnabled implements Cach
             }
         }
 
+        @Override
+        public V computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction) {
+            validateRecords();
+            return map.computeIfAbsent(key, k -> {
+                V v = mappingFunction.apply(k);
+                add(v);
+                return v;
+            });
+        }
     }
 }