Java集合之Vector

Vector是矢量队列，它继承了AbstractList，实现了List、 RandomAccess, Cloneable, java.io.Serializable接口。

Vector接口依赖图：

Vector继承了AbstractList，实现了List，它是一个队列，因此实现了相应的添加、删除、修改、遍历等功能。 Vector实现了RandomAccess接口，因此可以随机访问。 Vector实现了Cloneable，重载了clone()方法，因此可以进行克隆。 Vector实现了Serializable接口，因此可以进行序列化。 Vector的 操作是线程安全的。
Vector的数据结构和ArrayList差不多，包含了3个成员变量：elementData，elementCount，capacityIncrement。 （1）elementData是Object[]的数组，初始大小为10，会不断的增长。 （2）elementCount是元素的个数。 （3）capacityIncrement是动态数组增长的系数。
Vector有四种遍历方式： （1）第一种通过迭代器遍历，即通过Iterator去遍历                  

Integer value=null;
Iterator iter=vector.iterator();
while(iter.hasNext())
{
    value=(Interger)iter.next();
}

（2）第二种随机访问，通过索引进行遍历

Integer value=null;
int size=vector.size();
for(int i=0;i<size;i++)
{
value=vector.get(i);
}

（3）第三种通过for循环的方式

Integer value=null;
for( Integer inte： vector)
{
value=inte;
}

（4）第四种，Enumeration遍历   

Integer value=null;
Enumeration enu=vector.elements();
while(enu.hasMoreElements())
{
value=(Integer)enu.nextElement();
}

Vector示例代码：

public class Hello {

public static void main(String[] args) {
        Vector vec = new Vector();
//添加
vec.add("1");
vec.add("2");
vec.add("3");
vec.add("4");
vec.add("5");
//替换
vec.set(0, "100");
vec.add(2, "300");

System.out.println("vec:"+vec);
System.out.println("vec.indexOf(100):"+vec.indexOf("100"));
System.out.println("vec.lastIndexOf(100):"+vec.lastIndexOf("100"));
System.out.println("vec.firstElement():"+vec.firstElement());
System.out.println("vec.elementAt(2):"+vec.elementAt(2));
System.out.println("vec.lastElement():"+vec.lastElement());
System.out.println("size:"+vec.size());
System.out.println("capacity:"+vec.capacity());
System.out.println("vec 2 to 4:"+vec.subList(1, 4));
Enumeration enu = vec.elements();
        while(enu.hasMoreElements())
        {
            System.out.println("nextElement():"+enu.nextElement());
            Vector retainVec = new Vector();
            retainVec.add("100");
            retainVec.add("300");
            System.out.println("vec.retain():"+vec.retainAll(retainVec));
            System.out.println("vec:"+vec);
            String[] arr = (String[]) vec.toArray(new String[0]);
            for (String str:arr)
                System.out.println("str:"+str);
            vec.clear();
            vec.removeAllElements();
            System.out.println("vec.isEmpty():"+vec.isEmpty());
        }
    }
}

Vector源代码：

public class Vector<E> extends AbstractList<E>implements List<E>, RandomAccess, Cloneable, java.io.Serializable
{protected Object[] elementData;//对象数组，来存放数据
    protected int elementCount; //当前的数据数目
    protected int capacityIncrement; //容量增长
    private static final long serialVersionUID = -2767605614048989439L; //序列号
    //构造函数矢量队列初始化大小和增长大小
    public Vector(int initialCapacity, int capacityIncrement) {super();
        if (initialCapacity < 0)throw new IllegalArgumentException("Illegal Capacity: "+initialCapacity);
        this.elementData = new Object[initialCapacity];
        this.capacityIncrement = capacityIncrement;
    }//构造函数初始化大小
    public Vector(int initialCapacity) {this(initialCapacity, 0);
    }//构造函数默认初始化大小10
    public Vector() {this(10);
    }//带有集合参数的构造函数
    public Vector(Collectionextends 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);
    }//线程安全的对象数组拷贝
    public synchronized void copyInto(Object[] anArray) {System.arraycopy(elementData, 0, anArray, 0, elementCount);
    }//调整容量大小适合当前矢量队列的大小
    public synchronized void trimToSize() {modCount++;
        int oldCapacity = elementData.length;
        if (elementCount < oldCapacity) {elementData = Arrays.copyOf(elementData, elementCount);
        }}//增加矢量队列的容量大小
    public synchronized void ensureCapacity(int minCapacity) {if (minCapacity > 0) {modCount++;
            ensureCapacityHelper(minCapacity);
        }}private void ensureCapacityHelper(int minCapacity) {
// overflow-conscious code
        if (minCapacity - elementData.length > 0)grow(minCapacity);
    }private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
    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);
    }private static int hugeCapacity(int minCapacity) {if (minCapacity < 0) // overflow
            throw new OutOfMemoryError();
        return (minCapacity > MAX_ARRAY_SIZE) ?Integer.MAX_VALUE :MAX_ARRAY_SIZE;
    }//调整大小，如果超出了就删掉多余的对象
    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;
    }//矢量对象的容量
    public synchronized int capacity() {return elementData.length;
    }//矢量队列的大小
    public synchronized int size() {return elementCount;
    }//是否为空
    public synchronized boolean isEmpty() {return elementCount == 0;
    }//生成Enumeration对象，进行遍历
    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");
            }};
    }//判断是否包含某个对象
    public boolean contains(Object o) {return indexOf(o, 0) >= 0;
    }//返回某个对象的下标
    public int indexOf(Object o) {return indexOf(o, 0);
    }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;
    }//最后出现的对象的坐标
    public synchronized int lastIndexOf(Object o) {return lastIndexOf(o, elementCount-1);
    }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;
    }//返回某个坐标的节点
    public synchronized E elementAt(int index) {if (index >= elementCount) {throw new ArrayIndexOutOfBoundsException(index + " >= " + elementCount);
        }return elementData(index);
    }//第一个元素
    public synchronized E firstElement() {if (elementCount == 0) {throw new NoSuchElementException();
        }return elementData(0);
    }//最后一个元素
    public synchronized E lastElement() {if (elementCount == 0) {throw new NoSuchElementException();
        }return elementData(elementCount - 1);
    }//对下标为index的元素替换为obj
    public synchronized void setElementAt(E obj, int index) {if (index >= elementCount) {throw new ArrayIndexOutOfBoundsException(index + " >= " +elementCount);
        }elementData[index] = obj;
    }//删除某个下标的元素
    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--;
        elementData[elementCount] = null; /* to let gc do its work */
    }//在index坐标后添加obj
    public synchronized void insertElementAt(E obj, int index) {modCount++;
        if (index > elementCount) {throw new ArrayIndexOutOfBoundsException(index+ " > " + elementCount);
        }ensureCapacityHelper(elementCount + 1);
        System.arraycopy(elementData, index, elementData, index + 1, elementCount - index);
        elementData[index] = obj;
        elementCount++;
    }//矢量队列末尾添加元素
    public synchronized void addElement(E obj) {modCount++;
        ensureCapacityHelper(elementCount + 1);
        elementData[elementCount++] = obj;
    }//删除obj元素
    public synchronized boolean removeElement(Object obj) {modCount++;
        int i = indexOf(obj);
        if (i >= 0) {removeElementAt(i);
            return true;
        }return false;
    }//清空所有元素
    public synchronized void removeAllElements() {modCount++;
// Let gc do its work
        for (int i = 0; i < elementCount; i++)elementData[i] = null;

        elementCount = 0;
    }//克隆
    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(e);
        }}//生成数组
    public synchronized Object[] toArray() {return Arrays.copyOf(elementData, elementCount);
    }@SuppressWarnings("unchecked")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;
    }@SuppressWarnings("unchecked")E elementData(int index) {return (E) elementData[index];
    }//得到index的元素
    public synchronized E get(int index) {if (index >= elementCount)throw new ArrayIndexOutOfBoundsException(index);

        return elementData(index);
    }//将index元素替换成element
    public synchronized E set(int index, E element) {if (index >= elementCount)throw new ArrayIndexOutOfBoundsException(index);

        E oldValue = elementData(index);
        elementData[index] = element;
        return oldValue;
    }//矢量队列队尾添加元素
    public synchronized boolean add(E e) {modCount++;
        ensureCapacityHelper(elementCount + 1);
        elementData[elementCount++] = e;
        return true;
    }//删除对象
    public boolean remove(Object o) {return removeElement(o);
    }//在index处添加元素
    public void add(int index, E element) {insertElementAt(element, index);
    }//删除index处元素
    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;
    }//清空元素
    public void clear() {removeAllElements();
    }//判断Vector中是否含有所有的Collection
    public synchronized boolean containsAll(Collection c) {return super.containsAll(c);
    }//将Collection添加到矢量队列的队尾
    public synchronized boolean addAll(Collectionextends 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;
    }//删除包含Collection的元素
    public synchronized boolean removeAll(Collection c) {return super.removeAll(c);
    }//删除不存在Collection的元素
    public synchronized boolean retainAll(Collection c) {return super.retainAll(c);
    }//在某个index之后追加集合
    public synchronized boolean addAll(int index, Collectionextends 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;
    }//判断矢量队列是否相同
    public synchronized boolean equals(Object o) {return super.equals(o);
    }//返回hashCode
    public synchronized int hashCode() {return super.hashCode();
    }//
    public synchronized String toString() {return super.toString();
    }//切断
    public synchronized List<E> subList(int fromIndex, int toIndex) {return Collections.synchronizedList(super.subList(fromIndex, toIndex),
                this);
    }//删除范围
    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;
    }//序列化
    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();
    }//迭代
    public synchronized ListIterator<E> listIterator(int index) {if (index < 0 || index > elementCount)throw new IndexOutOfBoundsException("Index: "+index);
        return new ListItr(index);
    }public synchronized ListIterator<E> listIterator() {return new ListItr(0);
    }public synchronized Iterator<E> iterator() {return new Itr();
    }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);
            }}public void remove() {if (lastRet == -1)throw new IllegalStateException();
            synchronized (Vector.this) {checkForComodification();
                Vector.this.remove(lastRet);
                expectedModCount = modCount;
            }cursor = lastRet;
            lastRet = -1;
        }@Override
        public void forEachRemaining(Consumersuper E> action) {Objects.requireNonNull(action);
            synchronized (Vector.this) {final int size = elementCount;
                int i = cursor;
                if (i >= size) {return;
                }@SuppressWarnings("unchecked")final E[] elementData = (E[]) Vector.this.elementData;
                if (i >= elementData.length) {throw new ConcurrentModificationException();
                }while (i != size && modCount == expectedModCount) {action.accept(elementData[i++]);
                }
// update once at end of iteration to reduce heap write traffic
                cursor = i;
                lastRet = i - 1;
                checkForComodification();
            }}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;
        }}@Override
    public synchronized void forEach(Consumersuper E> action) {Objects.requireNonNull(action);
        final int expectedModCount = modCount;
        @SuppressWarnings("unchecked")final E[] elementData = (E[]) this.elementData;
        final int elementCount = this.elementCount;
        for (int i=0; modCount == expectedModCount && i < elementCount; i++) {action.accept(elementData[i]);
        }if (modCount != expectedModCount) {throw new ConcurrentModificationException();
        }}@Override
    @SuppressWarnings("unchecked")public synchronized boolean removeIf(Predicatesuper E> filter) {Objects.requireNonNull(filter);
// figure out which elements are to be removed
        // any exception thrown from the filter predicate at this stage
        // will leave the collection unmodified
        int removeCount = 0;
        final int size = elementCount;
        final BitSet removeSet = new BitSet(size);
        final int expectedModCount = modCount;
        for (int i=0; modCount == expectedModCount && i < size; i++) {@SuppressWarnings("unchecked")final E element = (E) elementData[i];
            if (filter.test(element)) {removeSet.set(i);
                removeCount++;
            }}if (modCount != expectedModCount) {throw new ConcurrentModificationException();
        }// shift surviving elements left over the spaces left by removed elements
        final boolean anyToRemove = removeCount > 0;
        if (anyToRemove) {final int newSize = size - removeCount;
            for (int i=0, j=0; (i < size) && (j < newSize); i++, j++) {i = removeSet.nextClearBit(i);
                elementData[j] = elementData[i];
            }for (int k=newSize; k < size; k++) {elementData[k] = null;  // Let gc do its work
            }elementCount = newSize;
            if (modCount != expectedModCount) {throw new ConcurrentModificationException();
            }modCount++;
        }return anyToRemove;
    }@Override
    @SuppressWarnings("unchecked")public synchronized void replaceAll(UnaryOperator<E> operator) {Objects.requireNonNull(operator);
        final int expectedModCount = modCount;
        final int size = elementCount;
        for (int i=0; modCount == expectedModCount && i < size; i++) {elementData[i] = operator.apply((E) elementData[i]);
        }if (modCount != expectedModCount) {throw new ConcurrentModificationException();
        }modCount++;
    }@SuppressWarnings("unchecked")@Override
    public synchronized void sort(Comparatorsuper E> c) {final int expectedModCount = modCount;
        Arrays.sort((E[]) elementData, 0, elementCount, c);
        if (modCount != expectedModCount) {throw new ConcurrentModificationException();
        }modCount++;
    }@Override
    public Spliterator<E> spliterator() {return new VectorSpliterator<>(this, null, 0, -1, 0);
    }/** Similar to ArrayList Spliterator */
    static final class VectorSpliterator<E> implements Spliterator<E> {private final Vector<E> list;
        private Object[] array;
        private int index; // current index, modified on advance/split
        private int fence; // -1 until used; then one past last index
        private int expectedModCount; // initialized when fence set

        /** Create new spliterator covering the given  range */
        VectorSpliterator(Vector<E> list, Object[] array, int origin, int fence,
                          int expectedModCount) {this.list = list;
            this.array = array;
            this.index = origin;
            this.fence = fence;
            this.expectedModCount = expectedModCount;
        }private int getFence() { // initialize on first use
            int hi;
            if ((hi = fence) < 0) {synchronized(list) {array = list.elementData;
                    expectedModCount = list.modCount;
                    hi = fence = list.elementCount;
                }}return hi;
        }public Spliterator<E> trySplit() {int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;
            return (lo >= mid) ? null :new VectorSpliterator<E>(list, array, lo, index = mid,
                            expectedModCount);
        }@SuppressWarnings("unchecked")public boolean tryAdvance(Consumersuper E> action) {int i;
            if (action == null)throw new NullPointerException();
            if (getFence() > (i = index)) {index = i + 1;
                action.accept((E)array[i]);
                if (list.modCount != expectedModCount)throw new ConcurrentModificationException();
                return true;
            }return false;
        }@SuppressWarnings("unchecked")public void forEachRemaining(Consumersuper E> action) {int i, hi; // hoist accesses and checks from loop
            Vector<E> lst; Object[] a;
            if (action == null)throw new NullPointerException();
            if ((lst = list) != null) {if ((hi = fence) < 0) {synchronized(lst) {expectedModCount = lst.modCount;
                        a = array = lst.elementData;
                        hi = fence = lst.elementCount;
                    }}else
                    a = array;
                if (a != null && (i = index) >= 0 && (index = hi) <= a.length) {while (i < hi)action.accept((E) a[i++]);
                    if (lst.modCount == expectedModCount)return;
                }}throw new ConcurrentModificationException();
        }public long estimateSize() {return (long) (getFence() - index);
        }public int characteristics() {return Spliterator.ORDERED | Spliterator.SIZED | Spliterator.SUBSIZED;
        }}
}

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