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Vector 详解

作者：凡人多烦事01 | 2024-03-15 19:12:07

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vector 详解

一、Vector简介：

（1）Vector可以实现可增长的对象数组。与数组一样，可以使用整数索引进行访问的组件。不过，Vector的大小是可以增加或者减小的，以便适应创建Vector后进行添加或者删除操作。

（2）同时Vector是线程安全的！底层使用的是synchronized进行加锁。

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

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（3）Vector实现List接口，继承AbstractList类，所以我们可以将其看做队列，支持相关的添加、删除、修改、遍历等功能。

Vector实现RandmoAccess接口，即提供了随机访问功能，提供提供快速访问功能。在Vector我们可以直接访问元素。

Vector 实现了Cloneable接口，支持clone()方法，可以被克隆。

Vector实现了Serializable接口，因此可以进行序列化。

（4）成员变量方面，Vector提供了elementData , elementCount， capacityIncrement三个成员变量。其中

  • elementData ：“Object[]类型的数组”，它保存了Vector中的元素，是一个动态数组，可以随着元素的增加而动态的增长，（具体增长方式在ensureCapacity方法中）。如果在初始化Vector时没有指定容器大小，则使用默认大小为10。

  • elementCount：Vector 对象中的元素个数。

  • capacityIncrement：向量的大小大于其容量时，容量自动增加的量。如果在创建Vector时，指定了capacityIncrement的大小，则每次当Vector中动态数组容量增加时，增加的大小都是capacityIncrement。如果容量的增量小于等于零，则每次需要增大容量时，向量的容量将增大一倍。

二、Vector遍历：

//第一种：通过下标进行随机访问
for(int i = 0 ; i < vec.size() ; i++){
        value = vec.get(i);
    }
 
//第二种：迭代器：
Iterator it = vec.iterator();
    while(it.hasNext()){
        value = it.next();
        //do something
    }
 
//第三种：for循环
for(Integer value:vec){
        //do something
    }
 
//第四种：Enumeration循环:
Vector vec = new Vector<>();
    Enumeration enu = vec.elements();
    while (enu.hasMoreElements()) {
        value = (Integer)enu.nextElement();
    }

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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());
		}
	}
}

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输出结果：

vec:[100, 2, 300, 3, 4, 5]
vec.indexOf(100):0
vec.lastIndexOf(100):0
vec.firstElement():100
vec.elementAt(2):300
vec.lastElement():5
size:6
capacity:10
vec 2 to 4:[2, 300, 3]
nextElement():100
vec.retain():true
vec:[100, 300]
str:100
str:300
vec.isEmpty():true

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三、源码解析：

1、add（E e）：添加元素

add(E e)：将指定元素添加到此向量的末尾。

public synchronized boolean add(E e) {
        modCount++;     
        ensureCapacityHelper(elementCount + 1);    //确认容器大小，如果超过容量则扩容操作
        elementData[elementCount++] = e;   //将e元素添加至末尾
        return true;
    }

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这个方法相对而言比较简单，具体过程就是先确认容器的大小，看是否需要进行扩容操作，然后将E元素添加到此向量的末尾。

private void ensureCapacityHelper(int minCapacity) {
        if (minCapacity - elementData.length > 0)
            grow(minCapacity);
    }
    
    /**
     * 进行扩容操作
     * 如果此向量的当前容量小于minCapacity，则通过将其内部数组替换为一个较大的数组俩增加其容量。
     * 新数据数组的大小等于原来的大小 + capacityIncrement。
     * 除非 capacityIncrement 的值小于等于零，在后一种情况下，新的容量将为原来容量的两倍。
     * 不过，如果此大小仍然小于 minCapacity，则新容量将为 minCapacity。
     */
    private void grow(int minCapacity) {
        int oldCapacity = elementData.length;     //当前容器大小
        /*
         * 新容器大小
         * 若容量增量系数(capacityIncrement) > 0，则将容器大小增加到capacityIncrement
         * 否则将容量增加一倍
         */
        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);
    }
    
    /**
     * 判断是否超出最大范围
     * MAX_ARRAY_SIZE：private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
     */
    private static int hugeCapacity(int minCapacity) {
        if (minCapacity < 0)
            throw new OutOfMemoryError();
        return (minCapacity > MAX_ARRAY_SIZE) ? Integer.MAX_VALUE : MAX_ARRAY_SIZE;
    }

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对于Vector整个的扩容过程，就是根据capacityIncrement确认扩容大小的，若capacityIncrement <= 0 则扩大一倍，否则扩大至capacityIncrement 。当然这个容量的最大范围为Integer.MAX_VALUE即，2^32 - 1，所以Vector并不是可以无限扩充的。

2、remove(Object o)：
/**
     * 从Vector容器中移除指定元素E
     */
    public boolean remove(Object o) {
        return removeElement(o);
    }
 
    public synchronized boolean removeElement(Object obj) {
        modCount++;
        int i = indexOf(obj);   //计算obj在Vector容器中位置
        if (i >= 0) {
            removeElementAt(i);   //移除
            return true;
        }
        return false;
    }
    
    public synchronized void removeElementAt(int index) {
        modCount++;     //修改次数+1
        if (index >= elementCount) {   //删除位置大于容器有效大小
            throw new ArrayIndexOutOfBoundsException(index + " >= " + elementCount);
        }
        else if (index < 0) {    //位置小于 < 0
            throw new ArrayIndexOutOfBoundsException(index);
        }
        int j = elementCount - index - 1;
        if (j > 0) {   
            //从指定源数组中复制一个数组，复制从指定的位置开始，到目标数组的指定位置结束。
            //也就是数组元素从j位置往前移
            System.arraycopy(elementData, index + 1, elementData, index, j);
        }
        elementCount--;   //容器中有效组件个数 - 1
        elementData[elementCount] = null;    //将向量的末尾位置设置为null
    }

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因为Vector底层是使用数组实现的，所以它的操作都是对数组进行操作，只不过其是可以随着元素的增加而动态的改变容量大小，其实现方法是是使用Arrays.copyOf方法将旧数据拷贝到一个新的大容量数组中。Vector的整个内部实现都比较简单，这里就不在重述了。

3、Vector 其他方法源代码：
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(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);
    }
    //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(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;
    }
    //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, 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(Consumer<? super 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(Consumer<? super 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(Predicate<? super 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(Comparator<? super 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(Consumer<? super 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(Consumer<? super 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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原文转自：

https://blog.csdn.net/chenssy/article/details/37520981

https://blog.csdn.net/qq924862077/article/details/48039567?utm_source=blogxgwz3

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