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  • Vector源码分析

    import java.util.List;
    import java.util.Vector;
    
    public class VectorTest {
        public static void main(String[] args) {
            List<String> 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.
         *
         * <p>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。

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  • 原文地址:https://www.cnblogs.com/vincent4code/p/4797763.html
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