【JAVA】五 JAVA集合 Collection Vector Stack

【JAVA】五 JAVA集合 Collection Vector Stack

Collection

Collection 已知子集

BeanContext, BeanContextServices, BlockingDeque<E>, BlockingQueue<E>, Deque<E>, 
List<E>,NavigableSet<E>, Queue<E>, Set<E>, SortedSet<E>, TransferQueue<E>

Vector

Vector 与 ArrayList LinkedList 同属于List子类 .
Vector线程安全的动态数组

Vector属性

public class Vector<E>
    extends AbstractList<E>
    implements List<E>, RandomAccess, Cloneable, java.io.Serializable
{
    /** * The array buffer into which the components of the vector are * stored. The capacity of the vector is the length of this array buffer, * and is at least large enough to contain all the vector's elements. * * <p>Any array elements following the last element in the Vector are null. * * @serial */
    protected Object[] elementData;

    /** * The number of valid components in this {@code Vector} object. * Components {@code elementData[0]} through * {@code elementData[elementCount-1]} are the actual items. * * @serial */
    protected int elementCount;

    /** * The amount by which the capacity of the vector is automatically * incremented when its size becomes greater than its capacity. If * the capacity increment is less than or equal to zero, the capacity * of the vector is doubled each time it needs to grow. * * @serial */
    protected int capacityIncrement;

    /** use serialVersionUID from JDK 1.0.2 for interoperability */
    private static final long serialVersionUID = -2767605614048989439L;
}

Vector构造方法

    /** * 构造一个指定初始容量和增加容量的vector。 * * @param initialCapacity the initial capacity of the vector * @param capacityIncrement the amount by which the capacity is * increased when the vector overflows * @throws IllegalArgumentException if the specified initial capacity * is negative */
    public Vector(int initialCapacity, int capacityIncrement) {
        super();
        if (initialCapacity < 0)
            throw new IllegalArgumentException("Illegal Capacity: "+
                                               initialCapacity);
        this.elementData = new Object[initialCapacity];
        this.capacityIncrement = capacityIncrement;
    }

    /** * 构造一个指定初始容量的vector * 以其容量增量为 0 。 * @param initialCapacity the initial capacity of the vector * @throws IllegalArgumentException if the specified initial capacity * is negative */
    public Vector(int initialCapacity) {
        this(initialCapacity, 0);
    }

    /** * 构造一个空vector * 其内部数据数组10个空间 * 及其容量增加为 0 。 */
    public Vector() {
        this(10);
    }

    /** * 接收一个Collection的子集,将子集转换为vector类型 * * @param c the collection whose elements are to be placed into this * vector * @throws NullPointerException if the specified collection is null * @since 1.2 */
    public Vector(Collection<? extends E> c) {
        elementData = c.toArray();
        elementCount = elementData.length;
        // c.toArray might (incorrectly) not return Object[] (see 6260652)
        if (elementData.getClass() != Object[].class)
            elementData = Arrays.copyOf(elementData, elementCount, Object[].class);
    }

Vector 线程安全

Vector简单理解为线程安全的ArrayList , 通过代码来看看Vector是如何实现线程安全的.

public synchronized void trimToSize()
public synchronized void ensureCapacity(int minCapacity) 
public synchronized int indexOf(Object o, int index) 
public synchronized int lastIndexOf(Object o)
public synchronized void removeElementAt(int index)
public synchronized E get(int index) 
public synchronized E set(int index, E element)
...

这里没有贴出方法的实现, 其实方法实现和ArrayList 一样 , Vector只是在声明方法时加入了synchronized关键字 .

Stack

Stack：后进先出，实现了一些栈基本操作的方法
（其实并不是只能后进先出，因为继承自Vector就会有很多父类的方法，从某种意义上来讲，不是一个栈）

public
class Stack<E> extends Vector<E> {
    /** * Creates an empty Stack. */
    public Stack() {
    }

    /** * 把一个项目添加到堆栈的顶部。 * * @param item the item to be pushed onto this stack. * @return the <code>item</code> argument. * @see java.util.Vector#addElement */
    public E push(E item) {
        addElement(item);

        return item;
    }

    /** * 删除这个堆栈的顶部的对象并返回对象。 * * @return The object at the top of this stack (the last item * of the <tt>Vector</tt> object). * @throws EmptyStackException if this stack is empty. */
    public synchronized E pop() {
        E       obj;
        int     len = size();

        obj = peek();
        removeElementAt(len - 1);

        return obj;
    }

    /** * 查看这个堆栈的顶部的对象。 * * @return the object at the top of this stack (the last item * of the <tt>Vector</tt> object). * @throws EmptyStackException if this stack is empty. */
    public synchronized E peek() {
        int     len = size();

        if (len == 0)
            throw new EmptyStackException();
        return elementAt(len - 1);
    }

    /** * Tests if this stack is empty. * * @return <code>true</code> if and only if this stack contains * no items; <code>false</code> otherwise. */
    public boolean empty() {
        return size() == 0;
    }

    /** * * 最上面查找对象 * 找到返回尾部位置 * 反之 -1 * * @param o the desired object. * @return the 1-based position from the top of the stack where * the object is located; the return value <code>-1</code> * indicates that the object is not on the stack. */
    public synchronized int search(Object o) {
        int i = lastIndexOf(o);

        if (i >= 0) {
            return size() - i;
        }
        return -1;
    }

    /** use serialVersionUID from JDK 1.0.2 for interoperability */
    private static final long serialVersionUID = 1224463164541339165L;
}