提升编程效率的利器: 解析Google Guava库之集合篇Multimap（二）

<dependency>  
    <groupId>com.google.guava</groupId>  
    <artifactId>guava</artifactId>  
    <version>30.1-jre</version> <!-- 请检查最新版本 -->  
</dependency>

import com.google.common.collect.*;  
  
import java.util.*;  
  
public class SocialNetwork {  
  
    public static void main(String[] args) {  
        // 使用ArrayListMultimap来保存用户的朋友列表，保留插入顺序  
        ArrayListMultimap<String, String> friendsByUser = ArrayListMultimap.create();  
          
        // 使用HashMultimap来保存用户对朋友的点赞，不保证顺序  
        HashMultimap<String, String> likesByUser = HashMultimap.create();  
          
        // 使用LinkedHashMultimap来保存用户的消息，保留插入顺序  
        LinkedHashMultimap<String, String> messagesByUser = LinkedHashMultimap.create();  
          
        // 使用TreeMultimap来保存用户的活动日志，按键（时间戳）排序  
        TreeMultimap<Long, String> activityLog = TreeMultimap.create();  
  
        // 添加一些朋友  
        friendsByUser.putAll("Alice", Arrays.asList("Bob", "Charlie", "David"));  
        friendsByUser.putAll("Bob", Arrays.asList("Alice", "Charlie"));  
        friendsByUser.put("Charlie", "David");  
  
        // 添加一些点赞  
        likesByUser.put("Alice", "Bob's post");  
        likesByUser.put("Alice", "Charlie's photo");  
        likesByUser.put("Bob", "Charlie's photo");  
        likesByUser.putAll("Charlie", Arrays.asList("Alice's status", "David's video"));  
  
        // 添加一些消息  
        messagesByUser.put("Alice", "Hi Bob!");  
        messagesByUser.put("Alice", "How are you Charlie?");  
        messagesByUser.put("Bob", "Charlie, where are you?");  
        messagesByUser.putAll("Charlie", Arrays.asList("Here I am!", "Alice, check this out!"));  
  
        // 添加一些活动日志（假设时间戳是简单的顺序数字）  
        activityLog.put(1L, "Alice added a new friend");  
        activityLog.put(2L, "Bob liked a photo");  
        activityLog.put(3L, "Charlie sent a message");  
  
        // 打印出Alice的朋友列表  
        System.out.println("Alice's friends: " + friendsByUser.get("Alice"));  
  
        // 打印出点赞了Charlie的照片的用户  
        for (String user : likesByUser.keys()) {  
            if (likesByUser.containsEntry(user, "Charlie's photo")) {  
                System.out.println(user + " liked Charlie's photo");  
            }  
        }  
  
        // 打印出Alice发送的所有消息  
        for (String message : messagesByUser.get("Alice")) {  
            System.out.println("Alice said: " + message);  
        }  
  
        // 打印出按时间顺序的所有活动日志  
        for (Map.Entry<Long, String> entry : activityLog.entries()) {  
            System.out.println("Timestamp: " + entry.getKey() + ", Event: " + entry.getValue());  
        }  
  
        // 假设我们想要移除Bob作为Alice的朋友  
        friendsByUser.remove("Alice", "Bob");  
  
        // 再次打印出Alice的朋友列表，确认Bob已被移除  
        System.out.println("Alice's friends after removing Bob: " + friendsByUser.get("Alice"));  
    }  
}

import com.google.common.collect.*;  
  
import java.util.Collections;  
  
public class SynchronizedMultimapExample {  
    public static void main(String[] args) {  
        // 创建一个非线程安全的 Multimap  
        Multimap<String, Integer> multimap = ArrayListMultimap.create();  
  
        // 获得一个线程安全的 Multimap  
        Multimap<String, Integer> synchronizedMultimap = Multimaps.synchronizedMultimap(multimap);  
  
        // 在多线程环境中安全地使用 synchronizedMultimap  
        // 注意：迭代时需要在 synchronized 块中进行  
        synchronized (synchronizedMultimap) {  
            for (Map.Entry<String, Integer> entry : synchronizedMultimap.entries()) {  
                System.out.println(entry.getKey() + " : " + entry.getValue());  
            }  
        }  
  
        // 添加元素  
        synchronizedMultimap.put("test", 1);  
        synchronizedMultimap.put("test", 2);  
        synchronizedMultimap.put("another", 3);  
  
        // 再次安全地迭代  
        synchronized (synchronizedMultimap) {  
            for (String key : synchronizedMultimap.keySet()) {  
                System.out.println(key + " : " + synchronizedMultimap.get(key));  
            }  
        }  
    }  
}

import com.google.common.collect.*;  
  
import java.util.Collection;  
import java.util.Map;  
  
public class CustomForwardingMultimap<K, V> extends ForwardingMultimap<K, V> {  
    private final Multimap<K, V> delegate;  
  
    public CustomForwardingMultimap(Multimap<K, V> delegate) {  
        this.delegate = delegate;  
    }  
  
    @Override  
    protected Multimap<K, V> delegate() {  
        return delegate;  
    }  
  
    @Override  
    public Multimap<K, V> putAll(K key, Iterable<? extends V> values) {  
        System.out.println("Adding values for key: " + key);  
        return super.putAll(key, values);  
    }  
  
    public static void main(String[] args) {  
        Multimap<String, Integer> multimap = ArrayListMultimap.create();  
        CustomForwardingMultimap<String, Integer> customMultimap = new CustomForwardingMultimap<>(multimap);  
          
        customMultimap.putAll("test", Arrays.asList(1, 2, 3));  
        System.out.println(customMultimap); // Outputs: {test=[1, 2, 3]}  
    }  
}