Vector实现了AbstractList抽象类和List接口,和ArrayList一样是基于Array存储的
Vector 是线程安全的,在大多数方法上存在synchronized关键字
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//Vector存放的元素,初始化默认长度为10protected Object[] elementData;//元素个数protected int elementCount;//每次扩容大小,默认为0protected int capacityIncrement;//构造函数，无指定初始化大小和无扩容大小public Vector() { this(10);}//构造函数，指定初始化大小和无扩容大小public Vector(int initialCapacity) { this(initialCapacity, 0);}//构造函数，指定初始化大小和扩容大小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,Collection集合public Vector(Collection<? extends E> c) { elementData = c.toArray(); elementCount = elementData.length; if (elementData.getClass() != Object[].class) elementData = Arrays.copyOf(elementData, elementCount, Object[].class); }//确保扩容的最小容量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);}//扩容private void grow(int minCapacity) { int oldCapacity = elementData.length; //当扩容大小为0的时候,扩容为原来的2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);}private static int hugeCapacity(int minCapacity) { if (minCapacity < 0) // overflow throw new OutOfMemoryError(); return (minCapacity > MAX_ARRAY_SIZE) ? Integer.MAX_VALUE : MAX_ARRAY_SIZE;} |
- ensureCapacity(int minCapacity)方法确保Vector的最小长度,当扩容2倍小于minCapacity时,扩容到minCapacity大小,minCapacity不能小于0
- 最大长度为2的31次方-1
设置大小
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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;} |
超过大小的被设置为Null
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public synchronized void copyInto(Object[] anArray) { System.arraycopy(elementData, 0, anArray, 0, elementCount);}public synchronized void trimToSize() { modCount++; int oldCapacity = elementData.length; if (elementCount < oldCapacity) { elementData = Arrays.copyOf(elementData, elementCount); }}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;} |
是否为空
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public synchronized boolean isEmpty() { return elementCount == 0;} |
设置索引上的元素
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public synchronized void setElementAt(E obj, int index) { if (index >= elementCount) { throw new ArrayIndexOutOfBoundsException(index + " >= " + elementCount); } elementData[index] = obj;} |
添加元素
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public synchronized void addElement(E obj) { modCount++; ensureCapacityHelper(elementCount + 1); elementData[elementCount++] = obj;} |
扩容
插入元素
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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++;} |
- 扩容
- 数组拷贝向索引后移动
- 删除为向前移动
删除元素
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public synchronized boolean removeElement(Object obj) { modCount++; int i = indexOf(obj); if (i >= 0) { removeElementAt(i); return true; } return false;} |
只能删除第一个
-我是签名----------------------------
这里只是一个签名
详解
以上所述是小编给大家介绍的Java中的Vector，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对服务器之家网站的支持！
原文链接：http://www.cnblogs.com/imeng/archive/2017/10/18/7687091.html
