java.util.Vector

類定義：這是一個具體類，可以被實例化

public class Vector<E> extends AbstractList<E> implements List<E>,RandomAccess,Cloneable,java,io.Serializable

構造方法

//初始化向量，給出初始榮來那個以及capacityIncrement（控制着向量需要增長時所要增長的量）
public Vector(int initialCapacity, int capacityIncrement) {
        super();
        if (initialCapacity < 0)
            throw new IllegalArgumentException("Illegal Capacity: "+
                                               initialCapacity);
        this.elementData = new Object[initialCapacity];
        this.capacityIncrement = capacityIncrement;
    }
    //初始化向量，默認初始capactityIncrement是0
public Vector(int initialCapacity) {
        this(initialCapacity, 0);
    }
    //初始化向量，默認容量是10
public Vector() {
        this(10);
    }
   //用一個集合初始化向量，初始容量剛好是c的大小，元素個數也是c的元素個數
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);
    }

域：

protected Object[] elementData;  //Vector存儲元素使用數組,Vector的存儲能力等於數組長度，數組長度至少要達到能包含Vector的所有元素

protected int elementCount;     // vector包含的元素個數（少於等於數組長度的）

//當向量的大小（size）要大於存儲能力capacity時，向量的capacity將會自動增大。如果capacityincrement小於等於0，那麼每當需要增長時，容量增加一倍。該變量控制每次增長的大小
protected int capacityIncrement; 

//最大數組容量爲:最大整數-8
 private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;

公共方法

//將向量元素拷貝到一個數組裏，向量數組中的第k個元素拷到anArray對應的索引k處
public synchronized void copyInto(Object[] anArray) {
        System.arraycopy(elementData, 0, anArray, 0, elementCount);
    }

//將向量容量變爲剛好等於大小。（刪除多餘的存儲空間）
public synchronized void trimToSize() {
        modCount++;
        int oldCapacity = elementData.length;
        if (elementCount < oldCapacity) {
            elementData = Arrays.copyOf(elementData, elementCount);
        }
    }
//確保向量容量爲最小容量，如果當前的向量容量小於minCapacity，則會將存儲數組擴容到向量大小加capacityIncrement.即新的存儲數組長度爲:size+capacityIncrement.但是如果capacityIncrement小於等於0，那麼擴充的容量直接是擴充前的兩倍。如果新的存儲數組長度還是小雨minCpacity，則將數組長度擴展到minCapacity
public synchronized void ensureCapacity(int minCapacity) {
        if (minCapacity > 0) {
            modCount++;
            ensureCapacityHelper(minCapacity);
        }
    }
//設置向量容量，如果新的向量容量大於元素個數，則擴充數組到newSize. 否則，保留數組前newSize-1個元素，返回newSize
public synchronized void setSize(int newSize) {
        modCount++;
        if (newSize > elementCount) {
            ensureCapacityHelper(newSize);
        } else {
            for (int i = newSize ; i < elementCount ; i++) {
                elementData[i] = null;
            }
        }
        elementCount = newSize;
    }

//返回向量容量
public synchronized int capacity() {
        return elementData.length;
    }
//返回元素個數
public synchronized int size() {
        return elementCount;
    }
//判斷向量是否爲空
public synchronized boolean isEmpty() {
        return elementCount == 0;
    }
//枚舉向量元素，從0~elementCount
public Enumeration<E> elements() {
        return new Enumeration<E>() {
            int count = 0;

            public boolean hasMoreElements() {
                return count < elementCount;
            }

            public E nextElement() {
                synchronized (Vector.this) {
                    if (count < elementCount) {
                        return elementData(count++);
                    }
                }
                throw new NoSuchElementException("Vector Enumeration");
            }
        };
    }
//判斷是否包含元素o
public boolean contains(Object o) {
        return indexOf(o, 0) >= 0;
    }
//返回元素o的位置
public int indexOf(Object o) {
        return indexOf(o, 0);
    }
//從index開始往後尋找，找到第一個等於o的元素並返回其索引，若沒有則返回-1
public synchronized int indexOf(Object o, int index) {
        if (o == null) {
            for (int i = index ; i < elementCount ; i++)
                if (elementData[i]==null)
                    return i;
        } else {
            for (int i = index ; i < elementCount ; i++)
                if (o.equals(elementData[i]))
                    return i;
        }
        return -1;
    }

//返回元素o在向量中最後出現的位置
  public synchronized int lastIndexOf(Object o) {
        return lastIndexOf(o, elementCount-1);
    }
 //從index開始往前查找，如果找到o,則返回其索引，否則返回-1.該方法是查找元素o在向量中最後出現的位置
public synchronized int lastIndexOf(Object o, int index) {
        if (index >= elementCount)
            throw new IndexOutOfBoundsException(index + " >= "+ elementCount);

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

//返回索引index處的元素。當給出的索引大於等於元素個數時，拋出數組越界異常。否則返回index處的值
 public synchronized E elementAt(int index) {
        if (index >= elementCount) {
            throw new ArrayIndexOutOfBoundsException(index + " >= " + elementCount);
        }

        return elementData(index);
    }

 //返回向量第一個元素
public synchronized E firstElement() {
        if (elementCount == 0) {
            throw new NoSuchElementException();
        }
        return elementData(0);
    }
//返回向量最後一個元素
public synchronized E lastElement() {
        if (elementCount == 0) {
            throw new NoSuchElementException();
        }
        return elementData(elementCount - 1);
    }
//設置index處的值
public synchronized void setElementAt(E obj, int index) {
        if (index >= elementCount) { //判斷Index是否合法
            throw new ArrayIndexOutOfBoundsException(index + " >= " +
                                                     elementCount);
        }
        elementData[index] = obj;
    }
//刪除index處的元素。首先判斷index的合法性，然後要將index之後的元素索引統一往前移一位，先計算要移動的元素個數，然後調用System.arraycopy(elementData, index + 1, elementData, index, j)將index+1之後的元素移動往前移一位。
public synchronized void removeElementAt(int index) {
        modCount++;
        if (index >= elementCount) {
            throw new ArrayIndexOutOfBoundsException(index + " >= " +
                                                     elementCount);
        }
        else if (index < 0) {
            throw new ArrayIndexOutOfBoundsException(index);
        }
        int j = elementCount - index - 1;
        if (j > 0) {
            System.arraycopy(elementData, index + 1, elementData, index, j);
        }
        elementCount--;   //元素個數減1
        elementData[elementCount] = null; /* to let gc do its work */將最後一個置空
    }
//在指定位置插入元素
public synchronized void insertElementAt(E obj, int index) {
        modCount++;
        if (index > elementCount) {
            throw new ArrayIndexOutOfBoundsException(index
                                                     + " > " + elementCount);
        }
        ensureCapacityHelper(elementCount + 1); //確保最小容量爲elementCount+1
        System.arraycopy(elementData, index, elementData, index + 1, elementCount - index);
        elementData[index] = obj;
        elementCount++;
    }
//添加一個元素到向量末尾
public synchronized void addElement(E obj) {
        modCount++;
        ensureCapacityHelper(elementCount + 1); //遇到添加元素時都要考慮容量大小
        elementData[elementCount++] = obj;
    }
//刪除向量中第一個等於obj的元素，如果有刪除，返回true,否則返回false
public synchronized boolean removeElement(Object obj) {
        modCount++;
        int i = indexOf(obj);
        if (i >= 0) {
            removeElementAt(i);
            return true;
        }
        return false;
    }

//刪除所有元素，將數組每個元素都置空，剩下就被垃圾回器回收。然後置elementCount=0
public synchronized void removeAllElements() {
        modCount++;
        // Let gc do its work
        for (int i = 0; i < elementCount; i++)
            elementData[i] = null;

        elementCount = 0;
    }
 //克隆一個新的向量，新向量內容等於原向量內容，新向量的存儲數組是新開闢出來的，並不是引用舊數組
 public synchronized Object clone() {
        try {
            @SuppressWarnings("unchecked")
                Vector<E> v = (Vector<E>) super.clone();
            v.elementData = Arrays.copyOf(elementData, elementCount);
            v.modCount = 0;
            return v;
        } catch (CloneNotSupportedException e) {
            // this shouldn't happen, since we are Cloneable
            throw new InternalError();
        }
    }

//返回向量的數組（只包含元素的那部分）
public synchronized Object[] toArray() {
        return Arrays.copyOf(elementData, elementCount);
    }
//將向量所有元素類型轉換爲T的a數組
public synchronized <T> T[] toArray(T[] a) {
        if (a.length < elementCount)
            return (T[]) Arrays.copyOf(elementData, elementCount, a.getClass());

        System.arraycopy(elementData, 0, a, 0, elementCount);

        if (a.length > elementCount)
            a[elementCount] = null;

        return a;
    }
//返回index處的元素
public synchronized E get(int index) {
        if (index >= elementCount)
            throw new ArrayIndexOutOfBoundsException(index);

        return elementData(index);
    }
//設置index處的值，並返回舊值
public synchronized E set(int index, E element) {
        if (index >= elementCount)
            throw new ArrayIndexOutOfBoundsException(index);

        E oldValue = elementData(index);
        elementData[index] = element;
        return oldValue;
    }
//添加一個元素e
public synchronized boolean add(E e) {
        modCount++;
        ensureCapacityHelper(elementCount + 1);
        elementData[elementCount++] = e;
        return true;
    }
  //刪除元素o
public boolean remove(Object o) {
        return removeElement(o);
    }

//在指定位置插入元素
public void add(int index, E element) {
        insertElementAt(element, index);
    }
//刪除指定位置的元素，並返回該元素
public synchronized E remove(int index) {
        modCount++;
        if (index >= elementCount)
            throw new ArrayIndexOutOfBoundsException(index);
        E oldValue = elementData(index);

        int numMoved = elementCount - index - 1;
        if (numMoved > 0)
            System.arraycopy(elementData, index+1, elementData, index,
                             numMoved);
        elementData[--elementCount] = null; // Let gc do its work

        return oldValue;
    }

//清空向量
  public void clear() {
        removeAllElements();
    }
    //判斷是否包含集合c
  public synchronized boolean containsAll(Collection<?> c) {
        return super.containsAll(c);
    }
//添加集合c，如果有添加返回true，否則返回false。
public synchronized boolean addAll(Collection<? extends E> c) {
        modCount++;
        Object[] a = c.toArray();
        int numNew = a.length;
        ensureCapacityHelper(elementCount + numNew);
        System.arraycopy(a, 0, elementData, elementCount, numNew);
        elementCount += numNew;
        return numNew != 0;
    }

//刪除在向量中同時也在c中的元素
 public synchronized boolean removeAll(Collection<?> c) {
        return super.removeAll(c);
    }
//刪除向量中不被c包含的元素
public synchronized boolean retainAll(Collection<?> c) {
        return super.retainAll(c);
    }
//將集合C插入向量中指定位置。先判斷index的合法性，然後確保向量容量足夠，然後將從index開始的元素向後移動numNew位，然後將集合c的數組拷貝到向量數組的index位置開始的空間.
public synchronized boolean addAll(int index, Collection<? extends E> c) {
        modCount++;
        if (index < 0 || index > elementCount)
            throw new ArrayIndexOutOfBoundsException(index);

        Object[] a = c.toArray();
        int numNew = a.length;
        ensureCapacityHelper(elementCount + numNew);

        int numMoved = elementCount - index;
        if (numMoved > 0)
            System.arraycopy(elementData, index, elementData, index + numNew,
                             numMoved);

        System.arraycopy(a, 0, elementData, index, numNew);
        elementCount += numNew;
        return numNew != 0;
    }

//判斷向量是否等於o
 public synchronized boolean equals(Object o) {
        return super.equals(o);
    }

public synchronized int hashCode() {
        return super.hashCode();
    }
public synchronized String toString() {
        return super.toString();
    }
//返回子集合
public synchronized List<E> subList(int fromIndex, int toIndex) {
        return Collections.synchronizedList(super.subList(fromIndex, toIndex),
                                            this);
    }
//刪除指定範圍內的集合，先計算要移動的個數，然後將toIndex之後的元素移動到fromIndex開始的位置，然後將剩餘空間置null
protected synchronized void removeRange(int fromIndex, int toIndex) {
        modCount++;
        int numMoved = elementCount - toIndex;
        System.arraycopy(elementData, toIndex, elementData, fromIndex,
                         numMoved);

        // Let gc do its work
        int newElementCount = elementCount - (toIndex-fromIndex);
        while (elementCount != newElementCount)
            elementData[--elementCount] = null;
    }
//返回集合的ListIterator,該ListIterator從index開始遍歷
public synchronized ListIterator<E> listIterator(int index) {
        if (index < 0 || index > elementCount)
            throw new IndexOutOfBoundsException("Index: "+index);
        return new ListItr(index);
    }
//返回集合的ListIterator,該ListIterator從0開始遍歷
public synchronized ListIterator<E> listIterator() {
        return new ListItr(0);
    }
//返回集合的迭代器
public synchronized Iterator<E> iterator() {
        return new Itr();
    }

私有方法

//如果最小容量大於數組當前的大小，則擴充數組
private void ensureCapacityHelper(int minCapacity) {
        // overflow-conscious code
        if (minCapacity - elementData.length > 0)
            grow(minCapacity);
    }

//擴展數組，主要是計算新數組的大小。如果capacityIncrement大於0，則新數組大小等於原數組大小加capacityIncrement,否則新數組大小是原來數組大小的兩倍。當新數組大小大於最大數組容量時，調用hugeCapacity
private void grow(int minCapacity) {
        // overflow-conscious code
        int oldCapacity = elementData.length;
        int newCapacity = oldCapacity + ((capacityIncrement > 0) ?
                                         capacityIncrement : oldCapacity);
        if (newCapacity - minCapacity < 0)
            newCapacity = minCapacity;
        if (newCapacity - MAX_ARRAY_SIZE > 0)
            newCapacity = hugeCapacity(minCapacity);
        elementData = Arrays.copyOf(elementData, newCapacity);
    }

//當最小容量小於0時，拋出異常，當最小容量大於最大數組容量時，返回最大整數，否則返回最大數組容量
private static int hugeCapacity(int minCapacity) {
        if (minCapacity < 0) // overflow
            throw new OutOfMemoryError();
        return (minCapacity > MAX_ARRAY_SIZE) ?
            Integer.MAX_VALUE :
            MAX_ARRAY_SIZE;
    }
//Save the state of the {@code Vector} instance to a stream
 private void writeObject(java.io.ObjectOutputStream s)
            throws java.io.IOException {
        final java.io.ObjectOutputStream.PutField fields = s.putFields();
        final Object[] data;
        synchronized (this) {
            fields.put("capacityIncrement", capacityIncrement);
            fields.put("elementCount", elementCount);
            data = elementData.clone();
        }
        fields.put("elementData", data);
        s.writeFields();
    }

私有類

 private class Itr implements Iterator<E> {
        int cursor;       // index of next element to return
        int lastRet = -1; // index of last element returned; -1 if no such
        int expectedModCount = modCount;

        public boolean hasNext() {
            // Racy but within spec, since modifications are checked
            // within or after synchronization in next/previous
            return cursor != elementCount;
        }

        public E next() {
            synchronized (Vector.this) {
                checkForComodification();
                int i = cursor;
                if (i >= elementCount)
                    throw new NoSuchElementException();
                cursor = i + 1;
                return elementData(lastRet = i);
            }
        }
       //刪除當前迭代到的元素
        public void remove() {
            if (lastRet == -1)
                throw new IllegalStateException();
            synchronized (Vector.this) {
                checkForComodification();
                Vector.this.remove(lastRet);
                expectedModCount = modCount;
            }
            cursor = lastRet;  //刪除之後cursor就不能向前走了。
            lastRet = -1;    //lastRet=-1確保不能重複刪除
        }

        final void checkForComodification() {
            if (modCount != expectedModCount)
                throw new ConcurrentModificationException();
        }
    }


final class ListItr extends Itr implements ListIterator<E> {
        ListItr(int index) {
            super();
            cursor = index;
        }

        public boolean hasPrevious() {
            return cursor != 0;
        }

        public int nextIndex() {
            return cursor;
        }

        public int previousIndex() {
            return cursor - 1;
        }

        public E previous() {
            synchronized (Vector.this) {
                checkForComodification();
                int i = cursor - 1;
                if (i < 0)
                    throw new NoSuchElementException();
                cursor = i;
                return elementData(lastRet = i);
            }
        }

        public void set(E e) {
            if (lastRet == -1)
                throw new IllegalStateException();
            synchronized (Vector.this) {
                checkForComodification();
                Vector.this.set(lastRet, e);
            }
        }

        public void add(E e) {
            int i = cursor;
            synchronized (Vector.this) {
                checkForComodification();
                Vector.this.add(i, e);
                expectedModCount = modCount;
            }
            cursor = i + 1;
            lastRet = -1;
        }
    }