java集合框架---ArrayList/Vector/LinkedList詳解

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); } } /** * Constructs an empty list with an initial capacity of ten. */
    public ArrayList() { this.elementData = DEFAULTCAPACITY_EMPTY_ELEMENTDATA; } /** * 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 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; } }

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

public synchronized boolean add(E e) { modCount++; ensureCapacityHelper(elementCount + 1); elementData[elementCount++] = e; return true; }

transient int size = 0; transient Node<E> first; 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; } }

public boolean add(E e) { linkLast(e); return true; } void linkLast(E e) { final Node<E> l = last;//指向鏈表尾部
        final Node<E> newNode = new Node<>(l, e, null);//以當前的尾部節點爲新節點的pre，建立新節點。
        last = newNode;//將鏈表尾部指向新節點
        if (l == null)//若是鏈表爲空，那麼新節點是頭節點也是尾節點
            first = newNode; else//鏈表不爲空，那麼將該結點做爲原鏈表尾部的next
            l.next = newNode; size++; modCount++; }

public E get(int index) { checkElementIndex(index);//檢查索引是否合法
        return node(index).item;//查找數據
    }