java固定大小队列的几种实现方式详解

<dependency>
   <groupId>cn.hutool</groupId>
   <artifactId>hutool-all</artifactId>
   <version>5.4.0</version>
</dependency>

// 初始化时指定大小
private final FixedLinkedHashMap<String, Integer> fixedLinkedHashMap = new FixedLinkedHashMap<>(LIST_SIZE);

// 其余写入和读取操作同LinkedHashMap类似
// 对于key，可以按照自己的业务需求填写
fixedLinkedHashMap.put(UUID.randomUUID().toString(), 1);

// 读取操作
// 获取元素个数
long size = fixedLinkedHashMap.values().size();
// 统计其中的总和
int sum = fixedLinkedHashMap.values().stream().mapToInt(value -> value).sum();

<dependency>
   <groupId>com.google.guava</groupId>
   <artifactId>guava</artifactId>
   <version>30.1.1-jre</version>
</dependency>

// 初始化时指定大小
private final EvictingQueue<Integer> evictingQueue = EvictingQueue.create(LIST_SIZE);

// 添加元素
evictingQueue.add(MOCK_EXCEPTION_COUNT);

// 读取元素
// 元素个数
size = evictingQueue.size();
// 统计其中的和
sum = evictingQueue.stream().mapToInt(value -> value).sum();

<dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>

// 初始化RedisTemplate
@Resource
private RedisTemplate<String, Integer> redisTemplate;


ListOperations<String, Integer> stringIntegerListOperations = redisTemplate.opsForList();
// LPUSH操作
stringIntegerListOperations.leftPush(REDIS_LIST_KEY, MOCK_EXCEPTION_COUNT);
// LTRIM
stringIntegerListOperations.trim(REDIS_LIST_KEY, 0, LIST_SIZE - 1);
// LRANGE操作
List<Integer> range = stringIntegerListOperations.range(REDIS_LIST_KEY, 0, LIST_SIZE - 1);

// 对结果操作
size = range.size();
sum = range.stream().mapToInt(value -> value).sum();

@Service
@Slf4j
public class FixedListScheduler {

  private static final int LIST_SIZE = 10;

  private static final int MOCK_EXCEPTION_COUNT = 1;

  private static final String REDIS_LIST_KEY = "redis_fixed_list";

  private final FixedLinkedHashMap<String, Integer> fixedLinkedHashMap = new FixedLinkedHashMap<>(LIST_SIZE);

  private final EvictingQueue<Integer> evictingQueue = EvictingQueue.create(LIST_SIZE);

  @Resource
  private RedisTemplate<String, Integer> redisTemplate;

  @Scheduled(cron = "*/1 * * * * ?")
  public void schedule() {
    fixedLinkedHashMap.put(UUID.randomUUID().toString(), MOCK_EXCEPTION_COUNT);

    long size = fixedLinkedHashMap.values().size();
    int sum = fixedLinkedHashMap.values().stream().mapToInt(value -> value).sum();

    log.info("fixedLinkedHashMap size:{}, sum:{}", size, sum);
    evictingQueue.add(MOCK_EXCEPTION_COUNT);
    size = evictingQueue.size();
    sum = evictingQueue.stream().mapToInt(value -> value).sum();
    log.info("evictingQueue size:{}, sum:{}", size, sum);

    ListOperations<String, Integer> stringIntegerListOperations = redisTemplate.opsForList();
    stringIntegerListOperations.leftPush(REDIS_LIST_KEY, MOCK_EXCEPTION_COUNT);
    stringIntegerListOperations.trim(REDIS_LIST_KEY, 0, LIST_SIZE - 1);

    List<Integer> range = stringIntegerListOperations.range(REDIS_LIST_KEY, 0, LIST_SIZE - 1);
    if (!CollectionUtils.isEmpty(range)) {
      sum = range.stream().mapToInt(value -> value).sum();
      log.info("redis FixedList size:{}, sum:{}", range.size(), sum);
    }
  }
}