java util包学习（5） Vector 源码分析

package java.util;public class Vector<E>    extends AbstractList<E>    implements List<E>, RandomAccess, Cloneable, java.io.Serializable{       protected Object[] elementData;       protected int elementCount;       protected int capacityIncrement;//增量    /** use serialVersionUID from JDK 1.0.2 for interoperability   java身份证*/    private static final long serialVersionUID = -2767605614048989439L;   //使用指定的初始容量和容量增量构造一个空的向量。    public Vector(int initialCapacity, int capacityIncrement) {super();//调用父类构造  个人认为这是一种规范 虽然 什么都不做吧        if (initialCapacity < 0)            throw new IllegalArgumentException("Illegal Capacity: "+                                               initialCapacity);this.elementData = new Object[initialCapacity];this.capacityIncrement = capacityIncrement;    }      public Vector(int initialCapacity) {this(initialCapacity, 0);    }       public Vector() {this(10);//建议自己设置的时候大一些。。    }       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);    }   //同步方法  复制到另一个数组中    public synchronized void copyInto(Object[] anArray) {System.arraycopy(elementData, 0, anArray, 0, elementCount);    }/*对此向量的容量进行微调，使其等于向量的当前大小。如果此向量的容量大于其当前大小，则通过将其内部数据数组（保存在字段 elementData 中）替换为一个较小的数组，从而将容量更改为等于当前大小。应用程序可以使用此操作最小化向量的存储。 */       public synchronized void trimToSize() {modCount++;int oldCapacity = elementData.length;if (elementCount < oldCapacity) {            elementData = Arrays.copyOf(elementData, elementCount);}    }       public synchronized void ensureCapacity(int minCapacity) {modCount++;ensureCapacityHelper(minCapacity);// 增加此向量的容量（如有必要），以确保其至少能够保存最小容量参数指定的组件数。    }       private void ensureCapacityHelper(int minCapacity) {int oldCapacity = elementData.length;if (minCapacity > oldCapacity) {    Object[] oldData = elementData;    int newCapacity = (capacityIncrement > 0) ?(oldCapacity + capacityIncrement) : (oldCapacity * 2);        if (newCapacity < minCapacity) {newCapacity = minCapacity;    }            elementData = Arrays.copyOf(elementData, newCapacity);}    }       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;    }        public synchronized int capacity() {return elementData.length;    }       public synchronized int size() {return elementCount;    }        public synchronized boolean isEmpty() {return elementCount == 0;    }       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 (E)elementData[count++];    }}throw new NoSuchElementException("Vector Enumeration");    }};    }        public boolean contains(Object o) {return indexOf(o, 0) >= 0;    }       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;    }       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;    }        public synchronized E elementAt(int index) {if (index >= elementCount) {    throw new ArrayIndexOutOfBoundsException(index + " >= " + elementCount);//超过了数组已有数据的范围  当然越界了}        return (E)elementData[index];    }        public synchronized E firstElement() {if (elementCount == 0) {    throw new NoSuchElementException();}return (E)elementData[0];    }       public synchronized E lastElement() {if (elementCount == 0) {    throw new NoSuchElementException();}return (E)elementData[elementCount - 1];    }       public synchronized void setElementAt(E obj, int index) {if (index >= elementCount) {    throw new ArrayIndexOutOfBoundsException(index + " >= " +     elementCount);}elementData[index] = obj;    }       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);//部分数据往前移}elementCount--;elementData[elementCount] = null; /* to let gc do its work */    }       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);//部分数据往后移elementData[index] = obj;elementCount++;    }       public synchronized void addElement(E obj) {modCount++;ensureCapacityHelper(elementCount + 1);elementData[elementCount++] = obj;    }       public synchronized boolean removeElement(Object obj) {modCount++;int i = indexOf(obj);if (i >= 0) {    removeElementAt(i);    return true;}return false;    }       public synchronized void removeAllElements() {        modCount++;// Let gc do its workfor (int i = 0; i < elementCount; i++)    elementData[i] = null;elementCount = 0;    }       public synchronized Object clone() {try {    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();}    }      public synchronized Object[] toArray() {        return Arrays.copyOf(elementData, elementCount);    }       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;    }       public synchronized E get(int index) {if (index >= elementCount)    throw new ArrayIndexOutOfBoundsException(index);return (E)elementData[index];    }        public synchronized E set(int index, E element) {if (index >= elementCount)    throw new ArrayIndexOutOfBoundsException(index);Object oldValue = elementData[index];elementData[index] = element;return (E)oldValue;    }       public synchronized boolean add(E e) {modCount++;ensureCapacityHelper(elementCount + 1);elementData[elementCount++] = e;        return true;    }        public boolean remove(Object o) {        return removeElement(o);    }       public void add(int index, E element) {        insertElementAt(element, index);//原来是插入    }       public synchronized E remove(int index) {modCount++;if (index >= elementCount)    throw new ArrayIndexOutOfBoundsException(index);Object 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 workreturn (E)oldValue;    }      public void clear() {        removeAllElements();    }       public synchronized boolean containsAll(Collection<?> c) {        return super.containsAll(c);    }       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;    }        public synchronized boolean removeAll(Collection<?> c) {        return super.removeAll(c);    }        public synchronized boolean retainAll(Collection<?> c)  {        return super.retainAll(c);    }        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;    }       public synchronized boolean equals(Object o) {        return super.equals(o);    }        public synchronized int hashCode() {        return super.hashCode();    }       public synchronized String toString() {        return super.toString();    }       public synchronized List<E> subList(int fromIndex, int toIndex) {        return Collections.synchronizedList(super.subList(fromIndex, toIndex),                                            this);    }       protected synchronized void removeRange(int fromIndex, int toIndex) {modCount++;int numMoved = elementCount - toIndex;        System.arraycopy(elementData, toIndex, elementData, fromIndex,                         numMoved);// Let gc do its workint newElementCount = elementCount - (toIndex-fromIndex);while (elementCount != newElementCount)    elementData[--elementCount] = null;    }       private synchronized void writeObject(java.io.ObjectOutputStream s)        throws java.io.IOException    {s.defaultWriteObject();    }}

代码看起来很长 其实很简单 就是一堆同步方法吧，，Vector 虽然不常用 但是 它是线程安全的 版本很老的一个类了