Vector和Arraylist的区别

<%! Vector v=new Vector();
int i=0;
ServletContext application;
synchronized void leaveWord(String s) { //留言方法
application=getServletContext();
i++;
v.add("No."+i+","+s);
application.setAttribute("Mess",v);
}
%>
</div>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    瞪眼一看，Vector 是啥？为什么不用 ArrayList 。基础差是该的，应该补了。
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    然后百度查了一下，得知 Vector 是线程安全的，ArrayList 是不安全的(效率高)。
</p>
<hr style="word-wrap:break-word;word-break:break-all;margin:0px 0px 5px;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);" />
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    下面是 来自&nbsp;<a class="PostIndex-authorName" style="font-size:15px;text-decoration:none;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;color:#2F889A;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px;outline-color:invert;padding-right:0px;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);" href="https://liuyanzhao.com/wp-content/themes/begin/inc/go.php?url=https://www.zhihu.com/people/13641283343" rel="noopener noreferrer" target="_blank">清浅池塘</a>&nbsp;的一篇文章，该博主的文章都很不错。下面转载一下
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    前几篇文章我们重点说了ArrayLIst，是时候放出这张图了。
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    <img class="size-full wp-image-6415 aligncenter" style="font-size:15px;max-width:100%;border-top:0px;height:auto;font-family:inherit;border-right:0px;vertical-align:middle;border-bottom:0px;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px auto 10px;display:block;outline-color:invert;padding-right:0px;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);" alt="Vector和Arraylist的区别" src="https://liuyanzhao.com/wp-content/uploads/2017/10/vector.png" width="600" height="436" sizes="(max-width: 600px) 100vw, 600px" srcset="https://liuyanzhao.com/wp-content/uploads/2017/10/vector.png 600w, https://liuyanzhao.com/wp-content/uploads/2017/10/vector-300x218.png 300w" data-original="https://liuyanzhao.com/wp-content/uploads/2017/10/vector.png" />
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    这张图里的内容对我们学习<a title="查看与 Java 相关的文章" style="font-size:15px;text-decoration:none;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;color:#2F889A;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px;outline-color:invert;padding-right:0px;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);" href="https://liuyanzhao.com/tag/java/" target="_blank">Java</a>来说，非常的重要，白色的部分是需要去了解的，黄色部分是我们要去重点了解的，不但要知道怎么去用，至少还需要读一次源码。绿色部分内容已经很少用了，但在面试题中有可能会问到，我们来看一个经常出现的面试题：<b style="font-size:15px;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px;outline-color:invert;padding-right:0px;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">Arraylist与Vector的区别是什么？</b>
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    <b style="font-size:15px;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px;outline-color:invert;padding-right:0px;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">首先我们给出标准答案：</b>
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    <b style="font-size:15px;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px;outline-color:invert;padding-right:0px;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">1、Vector是线程安全的，ArrayList不是线程安全的。</b>
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    <b style="font-size:15px;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px;outline-color:invert;padding-right:0px;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">2、ArrayList在底层数组不够用时在原来的基础上扩展0.5倍，Vector是扩展1倍。</b>
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    &nbsp;
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    <strong style="font-size:15px;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px;outline-color:invert;padding-right:0px;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">1、看上图Vector和ArrayList一样，都继承自List，来看一下Vector的源码</strong>
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    <img class="size-full wp-image-6416 aligncenter" style="font-size:15px;max-width:100%;border-top:0px;height:auto;font-family:inherit;border-right:0px;vertical-align:middle;border-bottom:0px;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px auto 10px;display:block;outline-color:invert;padding-right:0px;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);" alt="Vector和Arraylist的区别" src="https://liuyanzhao.com/wp-content/uploads/2017/10/v2.png" width="675" height="239" sizes="(max-width: 675px) 100vw, 675px" srcset="https://liuyanzhao.com/wp-content/uploads/2017/10/v2.png 675w, https://liuyanzhao.com/wp-content/uploads/2017/10/v2-300x106.png 300w" data-original="https://liuyanzhao.com/wp-content/uploads/2017/10/v2.png" />
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    实现了List接口，底层和ArrayList一样，都是数组来实现的。
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    &nbsp;
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    <strong style="font-size:15px;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px;outline-color:invert;padding-right:0px;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">2、分别看一下这两个类的add方法</strong>
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    首先来看ArrayList的add源码
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    <img class="alignnone size-full wp-image-7636" style="font-size:15px;max-width:100%;border-top:0px;height:auto;font-family:inherit;border-right:0px;vertical-align:middle;border-bottom:0px;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 10px;display:block;outline-color:invert;padding-right:0px;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);" alt="Vector和Arraylist的区别" src="https://liuyanzhao.com/wp-content/uploads/2017/10/v2-b19db72823330f12eed436798e816591_hd.jpg" width="681" height="99" sizes="(max-width: 681px) 100vw, 681px" srcset="https://liuyanzhao.com/wp-content/uploads/2017/10/v2-b19db72823330f12eed436798e816591_hd.jpg 681w, https://liuyanzhao.com/wp-content/uploads/2017/10/v2-b19db72823330f12eed436798e816591_hd-300x44.jpg 300w" data-original="https://liuyanzhao.com/wp-content/uploads/2017/10/v2-b19db72823330f12eed436798e816591_hd.jpg" />
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    &nbsp;
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    再看Vector的add源码
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    <img class="size-full wp-image-6418 aligncenter" style="font-size:15px;max-width:100%;border-top:0px;height:auto;font-family:inherit;border-right:0px;vertical-align:middle;border-bottom:0px;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px auto 10px;display:block;outline-color:invert;padding-right:0px;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);" alt="Vector和Arraylist的区别" src="https://liuyanzhao.com/wp-content/uploads/2017/10/v4.png" width="655" height="110" sizes="(max-width: 655px) 100vw, 655px" srcset="https://liuyanzhao.com/wp-content/uploads/2017/10/v4.png 655w, https://liuyanzhao.com/wp-content/uploads/2017/10/v4-300x50.png 300w" data-original="https://liuyanzhao.com/wp-content/uploads/2017/10/v4.png" />
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    方法实现都一样，就是加了一个synchronized的关键字，
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    &nbsp;
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    <strong style="font-size:15px;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px;outline-color:invert;padding-right:0px;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">3、再来看看两个类 remove 方法</strong>
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    先看ArrayList的remove方法
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    <img class="size-full wp-image-6419 aligncenter" style="font-size:15px;max-width:100%;border-top:0px;height:auto;font-family:inherit;border-right:0px;vertical-align:middle;border-bottom:0px;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px auto 10px;display:block;outline-color:invert;padding-right:0px;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);" alt="Vector和Arraylist的区别" src="https://liuyanzhao.com/wp-content/uploads/2017/10/v5.png" width="600" height="217" sizes="(max-width: 600px) 100vw, 600px" srcset="https://liuyanzhao.com/wp-content/uploads/2017/10/v5.png 600w, https://liuyanzhao.com/wp-content/uploads/2017/10/v5-300x109.png 300w" data-original="https://liuyanzhao.com/wp-content/uploads/2017/10/v5.png" />
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    &nbsp;
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    再看Vector的remove方法
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    <img class="size-full wp-image-6420 aligncenter" style="font-size:15px;max-width:100%;border-top:0px;height:auto;font-family:inherit;border-right:0px;vertical-align:middle;border-bottom:0px;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px auto 10px;display:block;outline-color:invert;padding-right:0px;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);" alt="Vector和Arraylist的区别" src="https://liuyanzhao.com/wp-content/uploads/2017/10/v6.png" width="664" height="234" sizes="(max-width: 664px) 100vw, 664px" srcset="https://liuyanzhao.com/wp-content/uploads/2017/10/v6.png 664w, https://liuyanzhao.com/wp-content/uploads/2017/10/v6-300x106.png 300w" data-original="https://liuyanzhao.com/wp-content/uploads/2017/10/v6.png" />
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    方法实现上也一样，就是多了一个synchronized关键字
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    &nbsp;
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    <strong style="font-size:15px;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px;outline-color:invert;padding-right:0px;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">4、再看看两个类的get方法</strong>
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    ArrayList的get方法
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    <img class="size-full wp-image-6421 aligncenter" style="font-size:15px;max-width:100%;border-top:0px;height:auto;font-family:inherit;border-right:0px;vertical-align:middle;border-bottom:0px;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px auto 10px;display:block;outline-color:invert;padding-right:0px;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);" alt="Vector和Arraylist的区别" src="https://liuyanzhao.com/wp-content/uploads/2017/10/v8.png" width="600" height="90" sizes="(max-width: 600px) 100vw, 600px" srcset="https://liuyanzhao.com/wp-content/uploads/2017/10/v8.png 600w, https://liuyanzhao.com/wp-content/uploads/2017/10/v8-300x45.png 300w" data-original="https://liuyanzhao.com/wp-content/uploads/2017/10/v8.png" />
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    &nbsp;
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    Vector的get方法
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    <img class="size-full wp-image-6422 aligncenter" style="font-size:15px;max-width:100%;border-top:0px;height:auto;font-family:inherit;border-right:0px;vertical-align:middle;border-bottom:0px;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px auto 10px;display:block;outline-color:invert;padding-right:0px;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);" alt="Vector和Arraylist的区别" src="https://liuyanzhao.com/wp-content/uploads/2017/10/v9.png" width="600" height="105" sizes="(max-width: 600px) 100vw, 600px" srcset="https://liuyanzhao.com/wp-content/uploads/2017/10/v9.png 600w, https://liuyanzhao.com/wp-content/uploads/2017/10/v9-300x53.png 300w" data-original="https://liuyanzhao.com/wp-content/uploads/2017/10/v9.png" />
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    &nbsp;
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    <strong style="font-size:15px;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px;outline-color:invert;padding-right:0px;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">5、再看看Vector的其它方法</strong>
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    <img class="size-full wp-image-6423 aligncenter" style="font-size:15px;max-width:100%;border-top:0px;height:auto;font-family:inherit;border-right:0px;vertical-align:middle;border-bottom:0px;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px auto 10px;display:block;outline-color:invert;padding-right:0px;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);" alt="Vector和Arraylist的区别" src="https://liuyanzhao.com/wp-content/uploads/2017/10/v10.png" width="661" height="292" sizes="(max-width: 661px) 100vw, 661px" srcset="https://liuyanzhao.com/wp-content/uploads/2017/10/v10.png 661w, https://liuyanzhao.com/wp-content/uploads/2017/10/v10-300x133.png 300w" data-original="https://liuyanzhao.com/wp-content/uploads/2017/10/v10.png" />
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    &nbsp;
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    无一例外，<b style="font-size:15px;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px;outline-color:invert;padding-right:0px;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">只要是关键性的操作，方法前面都加了synchronized关键字，来保证线程的安全性</b>。当执行synchronized修饰的方法前，系统会对该方法加一把锁，方法执行完成后释放锁，<b style="font-size:15px;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px;outline-color:invert;padding-right:0px;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">加锁和释放锁的这个过程，在系统中是有开销的，因此，</b>在单线程的环境中，Vector效率要差很多。（多线程环境不允许用ArrayList，需要做处理）。
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    至于底层数组的扩容区别，这里就不带着大家读源码了，有兴趣的朋友大家自己读吧，底层代码几乎是一样的，不同的只是计算后的新数组长度不一致。
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    <b style="font-size:15px;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px;outline-color:invert;padding-right:0px;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">和ArrayList和Vector一样，同样的类似关系的类还有HashMap和HashTable，StringBuilder和StringBuffer，后者是前者线程安全版本的实现。</b>希望以后大家在面试过程中，能说出个因为所以，而不是一味的去背面试题，唯有理解，无需再背。
</p>
<p style="font-size:15px;word-wrap:break-word;border-top:0px;font-family:inherit;border-right:0px;vertical-align:baseline;border-bottom:0px;word-break:break-all;outline-width:0px;padding-bottom:0px;padding-top:0px;outline-style:none;padding-left:0px;border-left:0px;margin:0px 0px 5px;outline-color:invert;padding-right:0px;text-indent:2em;-webkit-tap-highlight-color:rgba(255, 0, 0, 0);">
    注：关于线程安全性，后续文章会说，这里只是简单说这两个类不一样的地方。
</p>