Vector底层源码理解笔记

public abstract class AbstractList extends AbstractCollection{
    //操作数
    protected transient int modCount = 0;
}
public class Vector extends AbstractList implements List{
    //数组容器
    protected Object[] elementData;//new Object[10]
    //元素个数（相当于ArrayList的size）
    protected int elementCount;
    //容量增量
    protected int capacityIncrement;//0
    //数组最大容量
    private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
    
    public Vector() {
        this(10);
    }
    
    // initialCapacity - 10
    public Vector(int initialCapacity) {
        this(initialCapacity, 0);
    }
    
    //initialCapacity - 10
    //capacityIncrement - 0
    public Vector(int initialCapacity, int capacityIncrement) {
        super();
        if (initialCapacity < 0)
            throw new IllegalArgumentException("Illegal Capacity: "+
                                               initialCapacity);
        this.elementData = new Object[initialCapacity];
        this.capacityIncrement = capacityIncrement;
    }
    
    public synchronized boolean add(E e) {
        modCount++;
        ensureCapacityHelper(elementCount + 1);
        elementData[elementCount++] = e;
        return true;
    }
    
    private void ensureCapacityHelper(int minCapacity) {
        if (minCapacity - elementData.length > 0)
            grow(minCapacity);
    }
    
    // minCapacity - 11
    private void grow(int minCapacity) {
        // oldCapacity - 10
        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);
    }
}

1.Vector的底层数据结构？

一维数组

2.默认初始化容量？

10

3.数组最大容量？

Integer.MAX_VALUE-8

4.Vector的扩容机制？

判断 容量增量是否大于0，大于0，数组长度+容量增量

判断 容量增量是否大于0，小于等于0，数组长度*2

5.Vector的特点？

线程安全的