Specific code analysis of Vector in Java collection (picture)

Vector is a vector queue, which inherits AbstractList and implements List, RandomAccess, Cloneable, java.io.Serializableinterface.

Vector interface dependency graph:

Vector inherits AbstractList and implements List. It is a queue, so it implements the corresponding addition, Delete, modify, traverse and other functions.

Vector implements the RandomAccess interface, so it can be accessed randomly.

Vector implements Cloneable and overloads the clone() method, so it can be cloned.

Vector implements the Serializable interface, so it can be serialized.

Vector's operations are thread-safe .

Vector's data structure is similar to ArrayList, including 3 members Variables: elementData, elementCount, capacityIncrement.

(1) elementData is an array of Object[], with an initial size of 10 and will continue to grow.

(2) elementCount is the number of elements.

(3)capacityIncrement is the coefficient of dynamic array growth.

Vector has four traversal methods:

(1) The first is traversal through iterator, that is, traversal through Iterator                  

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

(2) The second kind of random access, traverse through index

Integer value=size=vector.size()(i=i<i value="vector.get(i)}</pre"></i><p style="font-family:微软雅黑; font-size:14px; line-height:21px; widows:auto"><br></p>##(3 ) The third way through <p style="font-family:微软雅黑; font-size:14px; line-height:21px; widows:auto">for loop<a href="http://www.php.cn/code/9672.html" target="_blank"></a></p><pre style="font-family:Consolas; widows:auto; color:rgb(169,183,198); font-size:13.5pt; background-color:rgb(43,43,43)" class="brush:java;toolbar:false;">Integer value=( Integer intevector)
{
value=inte}

(4) The fourth way, Enumeration traversal

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

Vector sample code:

Hello {

(String[] args) {
        Vector vec = Vector()vec.add()vec.add()vec.add()vec.add()vec.add()vec.set()vec.add()System..println(+vec)System..println(+vec.indexOf())System..println(+vec.lastIndexOf())System..println(+vec.firstElement())System..println(+vec.elementAt())System..println(+vec.lastElement())System..println(+vec.size())System..println(+vec.capacity())System..println(+vec.subList())Enumeration enu = vec.elements()(enu.hasMoreElements())
        {
            System..println(+enu.nextElement())            Vector retainVec = Vector()            retainVec.add()            retainVec.add()            System..println(+vec.retainAll(retainVec))            System..println(+vec)            String[] arr = (String[]) vec.toArray(String[])(String str:arr)
                System..println(+str)            vec.clear()            vec.removeAllElements()            System..println(+vec.isEmpty())        }
    }
}

Vector source code:

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&#39;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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