#10 effective java: item 7

effective-java/src/test/java/com/example/effectivejava/chapter01/item07/cache/PostRepositoryTest.java

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+package com.example.effectivejava.chapter01.item07.cache;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.*;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class PostRepositoryTest {
+
+    @Test
+    void cache() throws InterruptedException {
+        PostRepository postRepository = new PostRepository();
+        CacheKey key1 = new CacheKey(1);
+        postRepository.getPostById(key1);
+
+        assertFalse(postRepository.getCache().isEmpty());
+
+        key1 = null;
+        // TODO run gc
+        System.out.println("run gc");
+        System.gc();
+        System.out.println("wait");
+        Thread.sleep(3000L);
+
+        assertTrue(postRepository.getCache().isEmpty());
+    }
+
+    @Test
+    void backgroundThread() throws InterruptedException {
+        ScheduledExecutorService executor = Executors.newScheduledThreadPool(1);
+        PostRepository postRepository = new PostRepository();
+        CacheKey key1 = new CacheKey(1);
+        postRepository.getPostById(key1);
+
+        Runnable removeOldCache = () -> {
+            System.out.println("running removeOldCache task");
+            Map<CacheKey, Post> cache = postRepository.getCache();
+            Set<CacheKey> cacheKeys = cache.keySet();
+            Optional<CacheKey> key = cacheKeys.stream().min(Comparator.comparing(CacheKey::getCreated));
+            key.ifPresent((k) -> {
+                System.out.println("removing " + k);
+                cache.remove(k);
+            });
+        };
+
+        System.out.println("The time is : " + new Date());
+
+        executor.scheduleAtFixedRate(removeOldCache,
+                1, 3, TimeUnit.SECONDS);
+
+        Thread.sleep(20000L);
+
+        executor.shutdown();
+    }
+}

effective-java/src/test/java/com/example/effectivejava/chapter01/item07/listener/ChatRoomTest.java

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+package com.example.effectivejava.chapter01.item07.listener;
+
+import org.junit.jupiter.api.Test;
+
+import java.lang.ref.WeakReference;
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class ChatRoomTest {
+
+    @Test
+    void charRoom() throws InterruptedException {
+        ChatRoom chatRoom = new ChatRoom();
+        User user1 = new User();
+        User user2 = new User();
+
+        chatRoom.addUser(user1);
+        chatRoom.addUser(user2);
+
+        chatRoom.sendMessage("hello");
+
+        user1 = null;
+
+        System.gc();
+
+        Thread.sleep(5000L);
+
+        List<WeakReference<User>> users = chatRoom.getUsers();
+        assertEquals(1, users.size());
+    }
+}