static class StrongEntry<K, V> extends AbstractReferenceEntry<K, V> {
    final K key;

    StrongEntry(K key, int hash, @Nullable ReferenceEntry<K, V> next) {
      this.key = key;
      this.hash = hash;
      this.next = next;
    }

    @Override
    public K getKey() {
      return this.key;
    }

    // The code below is exactly the same for each entry type.

    final int hash;
    final @Nullable ReferenceEntry<K, V> next;
    volatile ValueReference<K, V> valueReference = unset();

 StrongAccessEntry(K key, int hash, @Nullable ReferenceEntry<K, V> next) {
      super(key, hash, next); // 继承了StrongEntry，并多了accessTime
    }

    // The code below is exactly the same for each access entry type.

    volatile long accessTime = Long.MAX_VALUE;

LoadingCache<Key, Graph> graphs = CacheBuilder.newBuilder()
      .maximumSize(10000) // 最大元素个数
      .expireAfterWrite(Duration.ofMinutes(10)) // 元素写入10分钟后期
      .removalListener(MY_LISTENER)  // 自定义的一个监听器
      .build(
          new CacheLoader<Key, Graph>() {  // 元素加载器，当查询元素不存在时，会自动调用该方法进行加载，然后再返回元素
            public Graph load(Key key) throws AnyException {
              return createExpensiveGraph(key);
            }
         });
 }

@Override
  public V put(K key, V value) {
    checkNotNull(key);
    checkNotNull(value);
    int hash = hash(key);   // 首先计算key的hash值，并根据hash选定segment，再调用segment的put方法
    return segmentFor(hash).put(key, hash, value, false);
  }

/**
   * Returns the segment that should be used for a key with the given hash.
   *
   * @param hash the hash code for the key
   * @return the segment
   */
  Segment<K, V> segmentFor(int hash) {
    // 
    return segments[(hash >>> segmentShift) & segmentMask];
  }

@Nullable
    V put(K key, int hash, V value, boolean onlyIfAbsent) {
      lock();  // 一开始先加锁
      try {
        long now = map.ticker.read(); // 当前时间，单位纳秒
        preWriteCleanup(now); // 删除过期元素

        int newCount = this.count + 1;
        if (newCount > this.threshold) { // 必要时先扩容
          expand();
          newCount = this.count + 1;
        }

        //  根据hash再定位在table中的位置
        AtomicReferenceArray<ReferenceEntry<K, V>> table = this.table;
        int index = hash & (table.length() - 1);
        // 取得table中对应位置的链表的首个元素
        ReferenceEntry<K, V> first = table.get(index);

        // 遍历该链表，如果已在链表中则更新值.
        for (ReferenceEntry<K, V> e = first; e != null; e = e.getNext()) {
          K entryKey = e.getKey();
          if (e.getHash() == hash
              && entryKey != null
              && map.keyEquivalence.equivalent(key, entryKey)) {
            // We found an existing entry.

            ValueReference<K, V> valueReference = e.getValueReference();
            V entryValue = valueReference.get();

            if (entryValue == null) {
              ++modCount;
              if (valueReference.isActive()) {
                enqueueNotification(
                    key, hash, entryValue, valueReference.getWeight(), RemovalCause.COLLECTED);
                setValue(e, key, value, now);
                newCount = this.count; // count remains unchanged
              } else {
                setValue(e, key, value, now);
                newCount = this.count + 1;
              }
              this.count = newCount; // write-volatile
              evictEntries(e);
              return null;
            } else if (onlyIfAbsent) {
              // Mimic
              // "if (!map.containsKey(key)) ...
              // else return map.get(key);
              recordLockedRead(e, now);
              return entryValue;
            } else {
              // clobber existing entry, count remains unchanged
              ++modCount;
              enqueueNotification(
                  key, hash, entryValue, valueReference.getWeight(), RemovalCause.REPLACED);
              setValue(e, key, value, now);
              evictEntries(e);
              return entryValue;
            }
          }
        }

        // 在链表中未找到，则创建一个新的元素，并添加在链表的头部，即2.6章节示例中的table[1]和entry1之间.
        ++modCount;// 链表更新操作次数加1
        ReferenceEntry<K, V> newEntry = newEntry(key, hash, first);
        setValue(newEntry, key, value, now);
        table.set(index, newEntry);// 添加到链表头部
        newCount = this.count + 1;
        this.count = newCount; // segment内的元素个数加1
        evictEntries(newEntry);
        return null;
      } finally {
        unlock();
        postWriteCleanup(); // 前面删除元素时，会把删除通知加入到队列中，在这里遍历删除通知队列并发出通知
      }
    }

public @Nullable V getIfPresent(Object key) {    // 和put一样，先对key做hash，再定位segment，然后调用get访问
    int hash = hash(checkNotNull(key));
    V value = segmentFor(hash).get(key, hash);
    if (value == null) {
      globalStatsCounter.recordMisses(1);
    } else {
      globalStatsCounter.recordHits(1);
    }
    return value;
  }

@Nullable
    V get(Object key, int hash) {
      try {
        if (count != 0) { // read-volatile
          long now = map.ticker.read();
         // 查询存活的元素
          ReferenceEntry<K, V> e = getLiveEntry(key, hash, now);
          if (e == null) {
            return null;
          }

          V value = e.getValueReference().get();
          if (value != null) {
            recordRead(e, now);
            // 检查是否需要刷新元素
            return scheduleRefresh(e, e.getKey(), hash, value, now, map.defaultLoader);
          }
         // 删除非强引用的队列，包含key队列和value队列
          tryDrainReferenceQueues();
        }
        return null;
      } finally {
        postReadCleanup();// 检查是否有过期元素待删除
      }
    }

@Nullable
    ReferenceEntry<K, V> getLiveEntry(Object key, int hash, long now) {
      ReferenceEntry<K, V> e = getEntry(key, hash);
      if (e == null) {
        return null;
      } else if (map.isExpired(e, now)) { // 检查元素是否过期
        tryExpireEntries(now);
        return null;
      }
      return e;
    }
@Nullable
    ReferenceEntry<K, V> getEntry(Object key, int hash) {
      // 根据hash定位table中位置的链表，并进行遍历，检查hash是否相等
      for (ReferenceEntry<K, V> e = getFirst(hash); e != null; e = e.getNext()) {
        if (e.getHash() != hash) {
          continue;
        }

        K entryKey = e.getKey();
        if (entryKey == null) { // 被垃圾回收期回收，清理引用队列
          tryDrainReferenceQueues();
          continue;
        }

        if (map.keyEquivalence.equivalent(key, entryKey)) {
          return e;
        }
      }

      return null;
    }

void postReadCleanup() {
     // DRAIN_THRESHOLD=63，即每读64次会执行一次清理操作
      if ((readCount.incrementAndGet() & DRAIN_THRESHOLD) == 0) {
        cleanUp();
      }
    }

V remove(Object key, int hash) {
      lock();  // 和put有些类似，先加锁，再搜索，然后从链表删除
      try {
        long now = map.ticker.read();
        preWriteCleanup(now);

        int newCount = this.count - 1;
        AtomicReferenceArray<ReferenceEntry<K, V>> table = this.table;
        int index = hash & (table.length() - 1);
        ReferenceEntry<K, V> first = table.get(index);

        for (ReferenceEntry<K, V> e = first; e != null; e = e.getNext()) {
          K entryKey = e.getKey();
          if (e.getHash() == hash
              && entryKey != null
              && map.keyEquivalence.equivalent(key, entryKey)) {
            ValueReference<K, V> valueReference = e.getValueReference();
            V entryValue = valueReference.get();

            RemovalCause cause;
            if (entryValue != null) {
              cause = RemovalCause.EXPLICIT;
            } else if (valueReference.isActive()) {
              cause = RemovalCause.COLLECTED;
            } else {
              // currently loading
              return null;
            }

            ++modCount;
            // 删除方法有些特别，看下面分析
            ReferenceEntry<K, V> newFirst =
                removeValueFromChain(first, e, entryKey, hash, entryValue, valueReference, cause);
            newCount = this.count - 1;
            table.set(index, newFirst);
            this.count = newCount; // write-volatile
            return entryValue;
          }
        }

        return null;
      } finally {
        unlock();
        postWriteCleanup();
      }
    }

// removeValueFromChain调用了removeEntryFromChain
@GuardedBy("this")
    @Nullable
    ReferenceEntry<K, V> removeEntryFromChain(
        ReferenceEntry<K, V> first, ReferenceEntry<K, V> entry) {
      int newCount = count;
      ReferenceEntry<K, V> newFirst = entry.getNext();
     // 删除元素时，没有直接从链表上面摘除，而是遍历first和entry之间的元素，并拷贝新建新的元素构建链表
      for (ReferenceEntry<K, V> e = first; e != entry; e = e.getNext()) {
        ReferenceEntry<K, V> next = copyEntry(e, newFirst);
        if (next != null) {
          newFirst = next;
        } else {
          removeCollectedEntry(e);
          newCount--;
        }
      }
      this.count = newCount;
      return newFirst;
    }

static class StrongEntry<K, V> extends AbstractReferenceEntry<K, V> {
    final K key;
    final int hash;
    final @Nullable ReferenceEntry<K, V> next;
    volatile ValueReference<K, V> valueReference = unset();
}

Cache<String, Integer> lcache = CacheBuilder.newBuilder()
                  .maximumSize(100)
                  .concurrencyLevel(Runtime.getRuntime().availableProcessors()*2) // 当前CPU核数*2
.expireAfterWrite(30, TimeUnit.SECONDS) .build();

// 赋值for(int i=0; i<10000; i++) {
    lcache.put(String.valueOf(i), i);
}
// 查询    
Integer value = lcache.getIfPresent("10");