transient Object[] elementData; 

private int size;

public ArrayList(int initialCapacity) {
    if (initialCapacity > 0) {
        this.elementData = new Object[initialCapacity];
    } else if (initialCapacity == 0) {
        this.elementData = EMPTY_ELEMENTDATA;
    } else {
        throw new IllegalArgumentException("Illegal Capacity: "+
                                           initialCapacity);
    }
}

public ArrayList() {
    this.elementData = DEFAULTCAPACITY_EMPTY_ELEMENTDATA; // 10
}

public ArrayList(Collection<? extends E> c) {
    elementData = c.toArray();
    if ((size = elementData.length) != 0) {
        // c.toArray might (incorrectly) not return Object[] (see 6260652)
        if (elementData.getClass() != Object[].class)
            elementData = Arrays.copyOf(elementData, size, Object[].class);
    } else {
        // replace with empty array.
        this.elementData = EMPTY_ELEMENTDATA;
    }
}

/**
 * Increases the capacity of this <tt>ArrayList</tt> instance, if
 * necessary, to ensure that it can hold at least the number of elements
 * specified by the minimum capacity argument.
 *
 * @param   minCapacity   the desired minimum capacity
 */
public void ensureCapacity(int minCapacity) {
    int minExpand = (elementData != DEFAULTCAPACITY_EMPTY_ELEMENTDATA)
        // any size if not default element table
        ? 0
        // larger than default for default empty table. It's already
        // supposed to be at default size.
        : DEFAULT_CAPACITY;

    if (minCapacity > minExpand) {
        ensureExplicitCapacity(minCapacity);
    }
}

private void ensureCapacityInternal(int minCapacity) {
    if (elementData == DEFAULTCAPACITY_EMPTY_ELEMENTDATA) {
        minCapacity = Math.max(DEFAULT_CAPACITY, minCapacity);
    }

    ensureExplicitCapacity(minCapacity);
}

private void ensureExplicitCapacity(int minCapacity) {
    modCount++;

    // overflow-conscious code
    if (minCapacity - elementData.length > 0)
        grow(minCapacity);
}

/**
 * The maximum size of array to allocate.
 * Some VMs reserve some header words in an array.
 * Attempts to allocate larger arrays may result in
 * OutOfMemoryError: Requested array size exceeds VM limit
 */
private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;

/**
 * Increases the capacity to ensure that it can hold at least the
 * number of elements specified by the minimum capacity argument.
 *
 * @param minCapacity the desired minimum capacity
 */
private void grow(int minCapacity) {
    // overflow-conscious code
    int oldCapacity = elementData.length;
    int newCapacity = oldCapacity + (oldCapacity >> 1);
    if (newCapacity - minCapacity < 0)
        newCapacity = minCapacity;
    if (newCapacity - MAX_ARRAY_SIZE > 0)
        newCapacity = hugeCapacity(minCapacity);
    // minCapacity is usually close to size, so this is a win:
    elementData = Arrays.copyOf(elementData, newCapacity);
}

private static int hugeCapacity(int minCapacity) {
    if (minCapacity < 0) // overflow
        throw new OutOfMemoryError();
    return (minCapacity > MAX_ARRAY_SIZE) ?
        Integer.MAX_VALUE :
        MAX_ARRAY_SIZE;
}

public boolean add(E e) {
    ensureCapacityInternal(size + 1);  // Increments modCount!!
    elementData[size++] = e;
    return true;
}

public void add(int index, E element) {
    rangeCheckForAdd(index);

    ensureCapacityInternal(size + 1);  // Increments modCount!!
    System.arraycopy(elementData, index, elementData, index + 1,
                     size - index);
    elementData[index] = element;
    size++;
}

/**
 * Trims the capacity of this <tt>ArrayList</tt> instance to be the
 * list's current size.  An application can use this operation to minimize
 * the storage of an <tt>ArrayList</tt> instance.
 */
public void trimToSize() {
    modCount++;
    if (size < elementData.length) {
        elementData = (size == 0)
          ? EMPTY_ELEMENTDATA
          : Arrays.copyOf(elementData, size);
    }
}

public int indexOf(Object o) {
    if (o == null) {
        for (int i = 0; i < size; i++)
            if (elementData[i]==null)
                return i;
    } else {
        for (int i = 0; i < size; i++)
            if (o.equals(elementData[i]))
                return i;
    }
    return -1;
}

public int lastIndexOf(Object o) {
    if (o == null) {
        for (int i = size-1; i >= 0; i--)
            if (elementData[i]==null)
                return i;
    } else {
        for (int i = size-1; i >= 0; i--)
            if (o.equals(elementData[i]))
                return i;
    }
    return -1;
}

transient int size = 0;

/**
 * Pointer to first node.
 * Invariant: (first == null && last == null) ||
 *            (first.prev == null && first.item != null)
 */
transient Node<E> first;

/**
 * Pointer to last node.
 * Invariant: (first == null && last == null) ||
 *            (last.next == null && last.item != null)
 */
transient Node<E> last;

private static class Node<E> {
    E item;
    Node<E> next;
    Node<E> prev;

    Node(Node<E> prev, E element, Node<E> next) {
        this.item = element;
        this.next = next;
        this.prev = prev;
    }
}

/**
 * Constructs an empty list.
 */
public LinkedList() {
}

/**
 * Constructs a list containing the elements of the specified
 * collection, in the order they are returned by the collection's
 * iterator.
 *
 * @param  c the collection whose elements are to be placed into this list
 * @throws NullPointerException if the specified collection is null
 */
public LinkedList(Collection<? extends E> c) {
    this();
    addAll(c);
}

/**
 * Returns the first element in this list.
 *
 * @return the first element in this list
 * @throws NoSuchElementException if this list is empty
 */
public E getFirst() {
    final Node<E> f = first;
    if (f == null)
        throw new NoSuchElementException();
    return f.item;
}

/**
 * Returns the last element in this list.
 *
 * @return the last element in this list
 * @throws NoSuchElementException if this list is empty
 */
public E getLast() {
    final Node<E> l = last;
    if (l == null)
        throw new NoSuchElementException();
    return l.item;
}

/**
 * Appends all of the elements in the specified collection to the end of
 * this list, in the order that they are returned by the specified
 * collection's iterator.  The behavior of this operation is undefined if
 * the specified collection is modified while the operation is in
 * progress.  (Note that this will occur if the specified collection is
 * this list, and it's nonempty.)
 *
 * @param c collection containing elements to be added to this list
 * @return {@code true} if this list changed as a result of the call
 * @throws NullPointerException if the specified collection is null
 */
public boolean addAll(Collection<? extends E> c) {
    return addAll(size, c);
}

/**
 * Inserts all of the elements in the specified collection into this
 * list, starting at the specified position.  Shifts the element
 * currently at that position (if any) and any subsequent elements to
 * the right (increases their indices).  The new elements will appear
 * in the list in the order that they are returned by the
 * specified collection's iterator.
 *
 * @param index index at which to insert the first element
 *              from the specified collection
 * @param c collection containing elements to be added to this list
 * @return {@code true} if this list changed as a result of the call
 * @throws IndexOutOfBoundsException {@inheritDoc}
 * @throws NullPointerException if the specified collection is null
 */
public boolean addAll(int index, Collection<? extends E> c) {
    checkPositionIndex(index);

    Object[] a = c.toArray();
    int numNew = a.length;
    if (numNew == 0)
        return false;

    Node<E> pred, succ;
    if (index == size) {
        succ = null;
        pred = last;
    } else {
        succ = node(index);
        pred = succ.prev;
    }

    for (Object o : a) {
        @SuppressWarnings("unchecked") E e = (E) o;
        Node<E> newNode = new Node<>(pred, e, null);
        if (pred == null)
            first = newNode;
        else
            pred.next = newNode;
        pred = newNode;
    }

    if (succ == null) {
        last = pred;
    } else {
        pred.next = succ;
        succ.prev = pred;
    }

    size += numNew;
    modCount++;
    return true;
}

/**
 * Removes all of the elements from this list.
 * The list will be empty after this call returns.
 */
public void clear() {
    // Clearing all of the links between nodes is "unnecessary", but:
    // - helps a generational GC if the discarded nodes inhabit
    //   more than one generation
    // - is sure to free memory even if there is a reachable Iterator
    for (Node<E> x = first; x != null; ) {
        Node<E> next = x.next;
        x.item = null;
        x.next = null;
        x.prev = null;
        x = next;
    }
    first = last = null;
    size = 0;
    modCount++;
}

public E get(int index) {
    checkElementIndex(index);
    return node(index).item;
}

public E set(int index, E element) {
    checkElementIndex(index);
    Node<E> x = node(index);
    E oldVal = x.item;
    x.item = element;
    return oldVal;
}

public void add(int index, E element) {
    checkPositionIndex(index);

    if (index == size)
        linkLast(element);
    else
        linkBefore(element, node(index));
}

public E remove(int index) {
    checkElementIndex(index);
    return unlink(node(index));
}

public int indexOf(Object o) {
    int index = 0;
    if (o == null) {
        for (Node<E> x = first; x != null; x = x.next) {
            if (x.item == null)
                return index;
            index++;
        }
    } else {
        for (Node<E> x = first; x != null; x = x.next) {
            if (o.equals(x.item))
                return index;
            index++;
        }
    }
    return -1;
}

//addFirst(E e)
public void addFirst(E e) {
    if (e == null)//不允许放入null
        throw new NullPointerException();
    elements[head = (head - 1) & (elements.length - 1)] = e;//2.下标是否越界
    if (head == tail)//1.空间是否够用
        doubleCapacity();//扩容
}

//offer(E e)
public boolean offer(E e) {
    if (e == null)//不允许放入null元素
        throw new NullPointerException();
    modCount++;
    int i = size;
    if (i >= queue.length)
        grow(i + 1);//自动扩容
    size = i + 1;
    if (i == 0)//队列原来为空，这是插入的第一个元素
        queue[0] = e;
    else
        siftUp(i, e);//调整
    return true;
}

//siftUp()
private void siftUp(int k, E x) {
    while (k > 0) {
        int parent = (k - 1) >>> 1;//parentNo = (nodeNo-1)/2
        Object e = queue[parent];
        if (comparator.compare(x, (E) e) >= 0)//调用比较器的比较方法
            break;
        queue[k] = e;
        k = parent;
    }
    queue[k] = x;
}

public E poll() {
    if (size == 0)
        return null;
    int s = --size;
    modCount++;
    E result = (E) queue[0];//0下标处的那个元素就是最小的那个
    E x = (E) queue[s];
    queue[s] = null;
    if (s != 0)
        siftDown(0, x);//调整
    return result;
}

//siftDown()
private void siftDown(int k, E x) {
    int half = size >>> 1;
    while (k < half) {
    	//首先找到左右孩子中较小的那个，记录到c里，并用child记录其下标
        int child = (k << 1) + 1;//leftNo = parentNo*2+1
        Object c = queue[child];
        int right = child + 1;
        if (right < size &&
            comparator.compare((E) c, (E) queue[right]) > 0)
            c = queue[child = right];
        if (comparator.compare(x, (E) c) <= 0)
            break;
        queue[k] = c;//然后用c取代原来的值
        k = child;
    }
    queue[k] = x;
}

//remove(Object o)
public boolean remove(Object o) {
	//通过遍历数组的方式找到第一个满足o.equals(queue[i])元素的下标
    int i = indexOf(o);
    if (i == -1)
        return false;
    int s = --size;
    if (s == i) //情况1
        queue[i] = null;
    else {
        E moved = (E) queue[s];
        queue[s] = null;
        siftDown(i, moved);//情况2
        ......
    }
    return true;
}

//getEntry()方法
final Entry<K,V> getEntry(Object key) {
	......
	int hash = (key == null) ? 0 : hash(key);
    for (Entry<K,V> e = table[hash&(table.length-1)];//得到冲突链表
         e != null; e = e.next) {//依次遍历冲突链表中的每个entry
        Object k;
        //依据equals()方法判断是否相等
        if (e.hash == hash &&
            ((k = e.key) == key || (key != null && key.equals(k))))
            return e;
    }
    return null;
}

//addEntry()
void addEntry(int hash, K key, V value, int bucketIndex) {
    if ((size >= threshold) && (null != table[bucketIndex])) {
        resize(2 * table.length);//自动扩容，并重新哈希
        hash = (null != key) ? hash(key) : 0;
        bucketIndex = hash & (table.length-1);//hash%table.length
    }
    //在冲突链表头部插入新的entry
    Entry<K,V> e = table[bucketIndex];
    table[bucketIndex] = new Entry<>(hash, key, value, e);
    size++;
}

//removeEntryForKey()
final Entry<K,V> removeEntryForKey(Object key) {
	......
	int hash = (key == null) ? 0 : hash(key);
    int i = indexFor(hash, table.length);//hash&(table.length-1)
    Entry<K,V> prev = table[i];//得到冲突链表
    Entry<K,V> e = prev;
    while (e != null) {//遍历冲突链表
        Entry<K,V> next = e.next;
        Object k;
        if (e.hash == hash &&
            ((k = e.key) == key || (key != null && key.equals(k)))) {//找到要删除的entry
            modCount++; size--;
            if (prev == e) table[i] = next;//删除的是冲突链表的第一个entry
            else prev.next = next;
            return e;
        }
        prev = e; e = next;
    }
    return e;
}

//HashSet是对HashMap的简单包装
public class HashSet<E>
{
	......
  //HashSet里面有一个HashMap
	private transient HashMap<E,Object> map;
    // Dummy value to associate with an Object in the backing Map
    private static final Object PRESENT = new Object();
    public HashSet() {
        map = new HashMap<>();
    }
    ......
    public boolean add(E e) {//简单的方法转换
        return map.put(e, PRESENT)==null;
    }
    ......
}

// LinkedHashMap.addEntry()
void addEntry(int hash, K key, V value, int bucketIndex) {
    if ((size >= threshold) && (null != table[bucketIndex])) {
        resize(2 * table.length);// 自动扩容，并重新哈希
        hash = (null != key) ? hash(key) : 0;
        bucketIndex = hash & (table.length-1);// hash%table.length
    }
    // 1.在冲突链表头部插入新的entry
    HashMap.Entry<K,V> old = table[bucketIndex];
    Entry<K,V> e = new Entry<>(hash, key, value, old);
    table[bucketIndex] = e;
    // 2.在双向链表的尾部插入新的entry
    e.addBefore(header);
    size++;
}

// LinkedHashMap.Entry.addBefor()，将this插入到existingEntry的前面
private void addBefore(Entry<K,V> existingEntry) {
    after  = existingEntry;
    before = existingEntry.before;
    before.after = this;
    after.before = this;
}

// LinkedHashMap.removeEntryForKey()，删除key值对应的entry
final Entry<K,V> removeEntryForKey(Object key) {
	......
	int hash = (key == null) ? 0 : hash(key);
    int i = indexFor(hash, table.length);// hash&(table.length-1)
    Entry<K,V> prev = table[i];// 得到冲突链表
    Entry<K,V> e = prev;
    while (e != null) {// 遍历冲突链表
        Entry<K,V> next = e.next;
        Object k;
        if (e.hash == hash &&
            ((k = e.key) == key || (key != null && key.equals(k)))) {// 找到要删除的entry
            modCount++; size--;
            // 1. 将e从对应bucket的冲突链表中删除
            if (prev == e) table[i] = next;
            else prev.next = next;
            // 2. 将e从双向链表中删除
            e.before.after = e.after;
            e.after.before = e.before;
            return e;
        }
        prev = e; e = next;
    }
    return e;
}

public class LinkedHashSet<E>
    extends HashSet<E>
    implements Set<E>, Cloneable, java.io.Serializable {
    ......
    // LinkedHashSet里面有一个LinkedHashMap
    public LinkedHashSet(int initialCapacity, float loadFactor) {
        map = new LinkedHashMap<>(initialCapacity, loadFactor);
    }
	......
    public boolean add(E e) {//简单的方法转换
        return map.put(e, PRESENT)==null;
    }
    ......
}

class FifoCache<K,V> extends LinkedHashMap<K,v> {
  private final int size;
  public FifoCache(int size){
    this.size = size;
  }
  
  @Override
  protected boolean removeEldestEntry(Map.Entry<K,V> eldest){
    return size() > size;
  }
}

// 寻找节点后继函数successor()
static <K,V> TreeMap.Entry<K,V> successor(Entry<K,V> t) {
    if (t == null)
        return null;
    else if (t.right != null) {// 1. t的右子树不空，则t的后继是其右子树中最小的那个元素
        Entry<K,V> p = t.right;
        while (p.left != null)
            p = p.left;
        return p;
    } else {// 2. t的右孩子为空，则t的后继是其第一个向左走的祖先
        Entry<K,V> p = t.parent;
        Entry<K,V> ch = t;
        while (p != null && ch == p.right) {
            ch = p;
            p = p.parent;
        }
        return p;
    }
}

//getEntry()方法
final Entry<K,V> getEntry(Object key) {
    ......
    if (key == null)//不允许key值为null
        throw new NullPointerException();
    Comparable<? super K> k = (Comparable<? super K>) key;//使用元素的自然顺序
    Entry<K,V> p = root;
    while (p != null) {
        int cmp = k.compareTo(p.key);
        if (cmp < 0)//向左找
            p = p.left;
        else if (cmp > 0)//向右找
            p = p.right;
        else
            return p;
    }
    return null;
}

public V put(K key, V value) {
	......
    int cmp;
    Entry<K,V> parent;
    if (key == null)
        throw new NullPointerException();
    Comparable<? super K> k = (Comparable<? super K>) key;//使用元素的自然顺序
    do {
        parent = t;
        cmp = k.compareTo(t.key);
        if (cmp < 0) t = t.left;//向左找
        else if (cmp > 0) t = t.right;//向右找
        else return t.setValue(value);
    } while (t != null);
    Entry<K,V> e = new Entry<>(key, value, parent);//创建并插入新的entry
    if (cmp < 0) parent.left = e;
    else parent.right = e;
    fixAfterInsertion(e);//调整
    size++;
    return null;
}

//红黑树调整函数fixAfterInsertion()
private void fixAfterInsertion(Entry<K,V> x) {
    x.color = RED;
    while (x != null && x != root && x.parent.color == RED) {
        if (parentOf(x) == leftOf(parentOf(parentOf(x)))) {
            Entry<K,V> y = rightOf(parentOf(parentOf(x)));
            if (colorOf(y) == RED) {
                setColor(parentOf(x), BLACK);              // 情况1
                setColor(y, BLACK);                        // 情况1
                setColor(parentOf(parentOf(x)), RED);      // 情况1
                x = parentOf(parentOf(x));                 // 情况1
            } else {
                if (x == rightOf(parentOf(x))) {
                    x = parentOf(x);                       // 情况2
                    rotateLeft(x);                         // 情况2
                }
                setColor(parentOf(x), BLACK);              // 情况3
                setColor(parentOf(parentOf(x)), RED);      // 情况3
                rotateRight(parentOf(parentOf(x)));        // 情况3
            }
        } else {
            Entry<K,V> y = leftOf(parentOf(parentOf(x)));
            if (colorOf(y) == RED) {
                setColor(parentOf(x), BLACK);              // 情况4
                setColor(y, BLACK);                        // 情况4
                setColor(parentOf(parentOf(x)), RED);      // 情况4
                x = parentOf(parentOf(x));                 // 情况4
            } else {
                if (x == leftOf(parentOf(x))) {
                    x = parentOf(x);                       // 情况5
                    rotateRight(x);                        // 情况5
                }
                setColor(parentOf(x), BLACK);              // 情况6
                setColor(parentOf(parentOf(x)), RED);      // 情况6
                rotateLeft(parentOf(parentOf(x)));         // 情况6
            }
        }
    }
    root.color = BLACK;
}

// 红黑树entry删除函数deleteEntry()
private void deleteEntry(Entry<K,V> p) {
    modCount++;
    size--;
    if (p.left != null && p.right != null) {// 2. 删除点p的左右子树都非空。
        Entry<K,V> s = successor(p);// 后继
        p.key = s.key;
        p.value = s.value;
        p = s;
    }
    Entry<K,V> replacement = (p.left != null ? p.left : p.right);
    if (replacement != null) {// 1. 删除点p只有一棵子树非空。
        replacement.parent = p.parent;
        if (p.parent == null)
            root = replacement;
        else if (p == p.parent.left)
            p.parent.left  = replacement;
        else
            p.parent.right = replacement;
        p.left = p.right = p.parent = null;
        if (p.color == BLACK)
            fixAfterDeletion(replacement);// 调整
    } else if (p.parent == null) {
        root = null;
    } else { // 1. 删除点p的左右子树都为空
        if (p.color == BLACK)
            fixAfterDeletion(p);// 调整
        if (p.parent != null) {
            if (p == p.parent.left)
                p.parent.left = null;
            else if (p == p.parent.right)
                p.parent.right = null;
            p.parent = null;
        }
    }
}

private void fixAfterDeletion(Entry<K,V> x) {
    while (x != root && colorOf(x) == BLACK) {
        if (x == leftOf(parentOf(x))) {
            Entry<K,V> sib = rightOf(parentOf(x));
            if (colorOf(sib) == RED) {
                setColor(sib, BLACK);                   // 情况1
                setColor(parentOf(x), RED);             // 情况1
                rotateLeft(parentOf(x));                // 情况1
                sib = rightOf(parentOf(x));             // 情况1
            }
            if (colorOf(leftOf(sib))  == BLACK &&
                colorOf(rightOf(sib)) == BLACK) {
                setColor(sib, RED);                     // 情况2
                x = parentOf(x);                        // 情况2
            } else {
                if (colorOf(rightOf(sib)) == BLACK) {
                    setColor(leftOf(sib), BLACK);       // 情况3
                    setColor(sib, RED);                 // 情况3
                    rotateRight(sib);                   // 情况3
                    sib = rightOf(parentOf(x));         // 情况3
                }
                setColor(sib, colorOf(parentOf(x)));    // 情况4
                setColor(parentOf(x), BLACK);           // 情况4
                setColor(rightOf(sib), BLACK);          // 情况4
                rotateLeft(parentOf(x));                // 情况4
                x = root;                               // 情况4
            }
        } else { // 跟前四种情况对称
            Entry<K,V> sib = leftOf(parentOf(x));
            if (colorOf(sib) == RED) {
                setColor(sib, BLACK);                   // 情况5
                setColor(parentOf(x), RED);             // 情况5
                rotateRight(parentOf(x));               // 情况5
                sib = leftOf(parentOf(x));              // 情况5
            }
            if (colorOf(rightOf(sib)) == BLACK &&
                colorOf(leftOf(sib)) == BLACK) {
                setColor(sib, RED);                     // 情况6
                x = parentOf(x);                        // 情况6
            } else {
                if (colorOf(leftOf(sib)) == BLACK) {
                    setColor(rightOf(sib), BLACK);      // 情况7
                    setColor(sib, RED);                 // 情况7
                    rotateLeft(sib);                    // 情况7
                    sib = leftOf(parentOf(x));          // 情况7
                }
                setColor(sib, colorOf(parentOf(x)));    // 情况8
                setColor(parentOf(x), BLACK);           // 情况8
                setColor(leftOf(sib), BLACK);           // 情况8
                rotateRight(parentOf(x));               // 情况8
                x = root;                               // 情况8
            }
        }
    }
    setColor(x, BLACK);
}

// TreeSet是对TreeMap的简单包装
public class TreeSet<E> extends AbstractSet<E>
    implements NavigableSet<E>, Cloneable, java.io.Serializable
{
	......
    private transient NavigableMap<E,Object> m;
    // Dummy value to associate with an Object in the backing Map
    private static final Object PRESENT = new Object();
    public TreeSet() {
        this.m = new TreeMap<E,Object>();// TreeSet里面有一个TreeMap
    }
    ......
    public boolean add(E e) {
        return m.put(e, PRESENT)==null;
    }
    ......
}

Set<Object> weakHashSet = Collections
  .newSetFromMap(new WeakHashMap<Object, Boolean>());

// Collections.newSetFromMap()用于将任何Map包装成一个Set
public static <E> Set<E> newSetFromMap(Map<E, Boolean> map) {
    return new SetFromMap<>(map);
}

private static class SetFromMap<E> extends AbstractSet<E>
    implements Set<E>, Serializable
{
    private final Map<E, Boolean> m;  // The backing map
    private transient Set<E> s;       // Its keySet
    SetFromMap(Map<E, Boolean> map) {
        if (!map.isEmpty())
            throw new IllegalArgumentException("Map is non-empty");
        m = map;
        s = map.keySet();
    }
    public void clear()               {        m.clear(); }
    public int size()                 { return m.size(); }
    public boolean isEmpty()          { return m.isEmpty(); }
    public boolean contains(Object o) { return m.containsKey(o); }
    public boolean remove(Object o)   { return m.remove(o) != null; }
    public boolean add(E e) { return m.put(e, Boolean.TRUE) == null; }
    public Iterator<E> iterator()     { return s.iterator(); }
    public Object[] toArray()         { return s.toArray(); }
    public <T> T[] toArray(T[] a)     { return s.toArray(a); }
    public String toString()          { return s.toString(); }
    public int hashCode()             { return s.hashCode(); }
    public boolean equals(Object o)   { return o == this || s.equals(o); }
    public boolean containsAll(Collection<?> c) {return s.containsAll(c);}
    public boolean removeAll(Collection<?> c)   {return s.removeAll(c);}
    public boolean retainAll(Collection<?> c)   {return s.retainAll(c);}
    // addAll is the only inherited implementation
    ......
}

// java.util.Collection部分源码
public interface Collection<E> extends Iterable<E> {

    // 省略其他代码

    @Override
    default Spliterator<E> spliterator() {
        return Spliterators.spliterator(this, 0);
    }

    default Stream<E> stream() {
        return StreamSupport.stream(spliterator(), false);
    }

    default Stream<E> parallelStream() {
        return StreamSupport.stream(spliterator(), true);
    }
}

// java.lang.Iterable部分源码
public interface Iterable<T> {

    // 省略其他代码

    default void forEach(Consumer<? super T> action) {
        Objects.requireNonNull(action);
        for (T t : this) {
            action.accept(t);
        }
    }

    default Spliterator<T> spliterator() {
        return Spliterators.spliteratorUnknownSize(iterator(), 0);
    }
}

// JDK1.7中的java.lang.Iterable
public interface Iterable<T> {

    Iterator<T> iterator();
}

// JDK1.7中的Iterable实现
public MyIterable<Long> implements Iterable<Long>{

    public Iterator<Long> iterator(){
         ....
    }
}

public interface Spliterator<T> {

    // 暂时省略其他代码

    boolean tryAdvance(Consumer<? super T> action);

    default void forEachRemaining(Consumer<? super T> action) {
        do { } while (tryAdvance(action));
    }

    Spliterator<T> trySplit();

    long estimateSize();

    default long getExactSizeIfKnown() {
        return (characteristics() & SIZED) == 0 ? -1L : estimateSize();
    }

    int characteristics();

    default boolean hasCharacteristics(int characteristics) {
        return (characteristics() & characteristics) == characteristics;
    }

    default Comparator<? super T> getComparator() {
        throw new IllegalStateException();
    }

    // 暂时省略其他代码
}

public static void main(String[] args) throws Exception {
    List<Integer> list = new ArrayList<>();
    list.add(2);
    list.add(1);
    list.add(3);
    Spliterator<Integer> spliterator = list.stream().spliterator();
    final AtomicInteger round = new AtomicInteger(1);
    final AtomicInteger loop = new AtomicInteger(1);
    while (spliterator.tryAdvance(num -> System.out.printf("第%d轮回调Action,值:%d\n", round.getAndIncrement(), num))) {
        System.out.printf("第%d轮循环\n", loop.getAndIncrement());
    }
}

// 控制台输出
第1轮回调Action,值:2
第1轮循环
第2轮回调Action,值:1
第2轮循环
第3轮回调Action,值:3
第3轮循环

public static void main(String[] args) {
    List<Integer> list = new ArrayList<>();
    list.add(2);
    list.add(1);
    list.add(3);
    Spliterator<Integer> spliterator = list.stream().spliterator();
    final AtomicInteger round = new AtomicInteger(1);
    spliterator.forEachRemaining(num -> System.out.printf("第%d轮回调Action,值:%d\n", round.getAndIncrement(), num));
}

// 控制台输出
第1轮回调Action,值:2
第2轮回调Action,值:1
第3轮回调Action,值:3

public static void main(String[] args) throws Exception {
    List<Integer> list = new ArrayList<>();
    list.add(2);
    list.add(3);
    list.add(4);
    list.add(1);
    Spliterator<Integer> first = list.stream().spliterator();
    Spliterator<Integer> second = first.trySplit();
    first.forEachRemaining(num -> {
        System.out.printf("first spliterator item: %d\n", num);
    });
    second.forEachRemaining(num -> {
        System.out.printf("second spliterator item: %d\n", num);
    });
}

// 控制台输出
first spliterator item: 4
first spliterator item: 1
second spliterator item: 2
second spliterator item: 3