Split or move java-collections-maps module (#7802)

java-collections-maps-2/src/test/java/com/baeldung/map/weakhashmap/WeakHashMapUnitTest.java

@@ -0,0 +1,72 @@
+package com.baeldung.map.weakhashmap;
+
+
+import org.junit.Test;
+
+import java.util.WeakHashMap;
+import java.util.concurrent.TimeUnit;
+
+import static com.jayway.awaitility.Awaitility.await;
+import static org.junit.Assert.assertTrue;
+
+public class WeakHashMapUnitTest {
+
+    @Test
+    public void givenWeakHashMap_whenCacheValueThatHasNoReferenceToIt_GCShouldReclaimThatObject() {
+        //given
+        WeakHashMap<UniqueImageName, BigImage> map = new WeakHashMap<>();
+        BigImage bigImage = new BigImage("image_id");
+        UniqueImageName imageName = new UniqueImageName("name_of_big_image");
+
+        map.put(imageName, bigImage);
+        assertTrue(map.containsKey(imageName));
+
+        //when big image key is not reference anywhere
+        imageName = null;
+        System.gc();
+
+        //then GC will finally reclaim that object
+        await().atMost(10, TimeUnit.SECONDS).until(map::isEmpty);
+    }
+
+    @Test
+    public void givenWeakHashMap_whenCacheValueThatHasNoReferenceToIt_GCShouldReclaimThatObjectButLeaveReferencedObject() {
+        //given
+        WeakHashMap<UniqueImageName, BigImage> map = new WeakHashMap<>();
+        BigImage bigImageFirst = new BigImage("foo");
+        UniqueImageName imageNameFirst = new UniqueImageName("name_of_big_image");
+
+        BigImage bigImageSecond = new BigImage("foo_2");
+        UniqueImageName imageNameSecond = new UniqueImageName("name_of_big_image_2");
+
+        map.put(imageNameFirst, bigImageFirst);
+        map.put(imageNameSecond, bigImageSecond);
+        assertTrue(map.containsKey(imageNameFirst));
+        assertTrue(map.containsKey(imageNameSecond));
+
+        //when
+        imageNameFirst = null;
+        System.gc();
+
+        //then
+        await().atMost(10, TimeUnit.SECONDS).until(() -> map.size() == 1);
+        await().atMost(10, TimeUnit.SECONDS).until(() -> map.containsKey(imageNameSecond));
+    }
+
+
+    class BigImage {
+        public final String imageId;
+
+        BigImage(String imageId) {
+            this.imageId = imageId;
+        }
+    }
+
+    class UniqueImageName {
+        public final String imageName;
+
+        UniqueImageName(String imageName) {
+            this.imageName = imageName;
+        }
+    }
+}