import java.util.List;import java.util.Vector;public class VectorTest {    public static void main(String[] args) {        List
    
      vector = new Vector<>();        vector.add("abc");    }}
    

查看Vector构造方法：

/**     * Constructs an empty vector so that its internal data array     * has size {@code 10} and its standard capacity increment is     * zero.     */    public Vector() {        this(10);    }

查看this(10)

/**     * Constructs an empty vector with the specified initial capacity and     * with its capacity increment equal to zero.     *     * @param   initialCapacity   the initial capacity of the vector     * @throws IllegalArgumentException if the specified initial capacity     *         is negative     */    public Vector(int initialCapacity) {        this(initialCapacity, 0);    }

再继续看this(initialCapacity,0)

/**     * Constructs an empty vector with the specified initial capacity and     * capacity increment.     *     * @param   initialCapacity     the initial capacity of the vector     * @param   capacityIncrement   the amount by which the capacity is     *                              increased when the vector overflows     * @throws IllegalArgumentException if the specified initial capacity     *         is negative     */    public Vector(int initialCapacity, int capacityIncrement) {        super();        if (initialCapacity < 0)            throw new IllegalArgumentException("Illegal Capacity: "+                                               initialCapacity);        this.elementData = new Object[initialCapacity];        this.capacityIncrement = capacityIncrement;    }

此时initialCapacity为10，capacityIncrement为0，this.elementData为对象数组

/**     * The array buffer into which the components of the vector are     * stored. The capacity of the vector is the length of this array buffer,     * and is at least large enough to contain all the vector's elements.     *     * 
Any array elements following the last element in the Vector are null.     *     * @serial     */    protected Object[] elementData;

所以Vector底层采用的是数组来存放元素的，大部分的public方法都是synchronized的。即同步的。使用不当会造成性能问题。

Vector和ArrayList底层数据结构都是数组。