HashMap

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public V put(K key, V value) {         // 1. 初始化         if (table == EMPTY_TABLE) {             inflateTable(threshold);         }         // 2. 允许key为null的put         if (key == null)             return putForNullKey(value);         // 3. 首先通过Hash计算Hash值，然后计算数组索引         int hash = hash(key);         int i = indexFor(hash, table.length);         // 4. 处理冲突，遍历链表重新设置新值返回老值         for (Entry<K,V> e = table[i]; e != null; e = e.next) {             Object k;             if (e.hash == hash && ((k = e.key) == key || key.equals(k))) {                 V oldValue = e.value;                 e.value = value;                 e.recordAccess(this);                 return oldValue;             }         }         // 5. 无冲突，增加新值         modCount++;         addEntry(hash, key, value, i);         return null;     }   void addEntry(int hash, K key, V value, int bucketIndex) {     // 1. 超过指定阀值进行扩容处理     if ((size >= threshold) && (null != table[bucketIndex])) {         resize(2 * table.length);         hash = (null != key) ? hash(key) : 0;         bucketIndex = indexFor(hash, table.length);     }     // 2. 创建数组对应的值     createEntry(hash, key, value, bucketIndex); }   void createEntry(int hash, K key, V value, int bucketIndex) {     Entry<K,V> e = table[bucketIndex];     table[bucketIndex] = new Entry<>(hash, key, value, e);     size++; }