Java复习之集合框架总结

 public V put(K key, V value) {    return putVal(hash(key), key, value, false, true);  }final V putVal(int hash, K key, V value, boolean onlyIfAbsent,          boolean evict) {    Node<K,V>[] tab; Node<K,V> p; int n, i;    if ((tab = table) == null || (n = tab.length) == 0)      n = (tab = resize()).length;    if ((p = tab[i = (n - 1) & hash]) == null)      tab[i] = newNode(hash, key, value, null);    else {      Node<K,V> e; K k;      if (p.hash == hash &&        ((k = p.key) == key || (key != null && key.equals(k))))        e = p;      else if (p instanceof TreeNode)        e = ((TreeNode<K,V>)p).putTreeVal(this, tab, hash, key, value);      else {        for (int binCount = 0; ; ++binCount) {          if ((e = p.next) == null) {            p.next = newNode(hash, key, value, null);            if (binCount >= TREEIFY_THRESHOLD - 1) // -1 for 1st              treeifyBin(tab, hash);            break;          }          if (e.hash == hash &&            ((k = e.key) == key || (key != null && key.equals(k))))            break;          p = e;        }      }      if (e != null) { // existing mapping for key        V oldValue = e.value;        if (!onlyIfAbsent || oldValue == null)          e.value = value;        afterNodeAccess(e);        return oldValue;      }    }    ++modCount;    if (++size > threshold)      resize();    afterNodeInsertion(evict);    return null;  }public boolean add(E e) {    return map.put(e, PRESENT)==null;  }// PRESENT是一个Object 对象 private static final Object PRESENT = new Object();