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【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;
}