android-ImageLoader（转载于收藏）

最新推荐文章于 2018-10-12 14:30:04 发布

转载最新推荐文章于 2018-10-12 14:30:04 发布 · 340 阅读

Android 编程专栏收录该内容

354 篇文章

订阅专栏

本文详细解析了ImageLoader中三种下载器的实现原理，包括BaseImageDownloader、NetworkDeniedImageDownloader和SlowNetworkImageDownloader。针对不同网络状况和数据源类型，介绍了它们如何处理HTTP、HTTPS、文件、Content Provider等资源。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

下载器实现
1. ImageLoader中实现了三种的下载器：BaseImageDownloader、NetworkDeniedImageDownloader、SlowNetworkImageDownloader(都实现了接口ImageDownloader)
2. ImageDownloader接口中，实现了Scheme类，用于判断传入的一个Uri是什么Schme和其他操作。
Scheme分为：HTTP(“http”), HTTPS(“https”), FILE(“file”), CONTENT(“content”), ASSETS(“assets”), DRAWABLE(“drawable”), UNKNOWN(“”)。
3.▲NetworkDeniedImageDownloader下载器，因为网络不能接触，所以就不处理”http”和”https” 这两种需要网络的Scheme。

<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">NetworkDeniedImageDownloader</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">implements</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">ImageDownloader</span> {</span>

        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> ImageDownloader wrappedDownloader;

        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-title" style="box-sizing: border-box;">NetworkDeniedImageDownloader</span>(ImageDownloader wrappedDownloader) {
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.wrappedDownloader = wrappedDownloader;
        }

        <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span>
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> InputStream <span class="hljs-title" style="box-sizing: border-box;">getStream</span>(String imageUri, Object extra) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throws</span> IOException {
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">switch</span> (Scheme.ofUri(imageUri)) {
                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> HTTP:
                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> HTTPS:
                    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throw</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> IllegalStateException();
                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">default</span>:
                    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> wrappedDownloader.getStream(imageUri, extra);
            }
        }
    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li></ul>

▲SlowNetworkImageDownloader下载器，考虑到网络情况是属于比较差的，所以需要用到的InputStream来处理Scheme为”http”和”https”的Uri。

<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">SlowNetworkImageDownloader</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">implements</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">ImageDownloader</span> {</span>

        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> ImageDownloader wrappedDownloader;

        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-title" style="box-sizing: border-box;">SlowNetworkImageDownloader</span>(ImageDownloader wrappedDownloader) {
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.wrappedDownloader = wrappedDownloader;
        }

        <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span>
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> InputStream <span class="hljs-title" style="box-sizing: border-box;">getStream</span>(String imageUri, Object extra) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throws</span> IOException {
            InputStream imageStream = wrappedDownloader.getStream(imageUri, extra);
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">switch</span> (Scheme.ofUri(imageUri)) {
                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> HTTP:
                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> HTTPS:
                    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> FlushedInputStream(imageStream);
                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">default</span>:
                    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> imageStream;
            }
        }
    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li></ul>

▲BaseImageDownloader：此下载器最为重要，这个类里面写了ImageLoader处理各种数据源时是如何下载图片资源的。这边分别对所有的Scheme将对应的处理函数贴出来，有兴趣的网友再自行去看哈。这个其实可以抽出来作为自己的一个图片下载类，因为所有不同来源的图片下载方式都有。

<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">    <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span>
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> InputStream <span class="hljs-title" style="box-sizing: border-box;">getStream</span>(String imageUri, Object extra) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throws</span> IOException {
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">switch</span> (Scheme.ofUri(imageUri)) {
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> HTTP:
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> HTTPS:
                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> getStreamFromNetwork(imageUri, extra);
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> FILE:
                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> getStreamFromFile(imageUri, extra);
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> CONTENT:
                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> getStreamFromContent(imageUri, extra);
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> ASSETS:
                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> getStreamFromAssets(imageUri, extra);
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> DRAWABLE:
                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> getStreamFromDrawable(imageUri, extra);
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> UNKNOWN:
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">default</span>:
                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> getStreamFromOtherSource(imageUri, extra);
        }
    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li></ul>

网络图片，Http和Https的下载处理：

<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">protected</span> HttpURLConnection <span class="hljs-title" style="box-sizing: border-box;">createConnection</span>(String url, Object extra) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throws</span> IOException {
        String encodedUrl = Uri.encode(url, ALLOWED_URI_CHARS);
        HttpURLConnection conn = (HttpURLConnection) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> URL(encodedUrl).openConnection();
        conn.setConnectTimeout(connectTimeout);
        conn.setReadTimeout(readTimeout);
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> conn;
    }

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">protected</span> InputStream <span class="hljs-title" style="box-sizing: border-box;">getStreamFromNetwork</span>(String imageUri, Object extra) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throws</span> IOException {
        HttpURLConnection conn = createConnection(imageUri, extra);

        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> redirectCount = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>;
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">while</span> (conn.getResponseCode() / <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">100</span> == <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">3</span> && redirectCount < MAX_REDIRECT_COUNT) {
            conn = createConnection(conn.getHeaderField(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Location"</span>), extra);
            redirectCount++;
        }

        InputStream imageStream;
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">try</span> {
            imageStream = conn.getInputStream();
        } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">catch</span> (IOException e) {
            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Read all data to allow reuse connection (http://bit.ly/1ad35PY)</span>
            IoUtils.readAndCloseStream(conn.getErrorStream());
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throw</span> e;
        }
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (!shouldBeProcessed(conn)) {
            IoUtils.closeSilently(imageStream);
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throw</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> IOException(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Image request failed with response code "</span> + conn.getResponseCode());
        }

        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ContentLengthInputStream(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> BufferedInputStream(imageStream, BUFFER_SIZE), conn.getContentLength());
    }
</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li></ul>

来自本地文件，Scheme为”file”的下载处理：

<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">protected</span> InputStream <span class="hljs-title" style="box-sizing: border-box;">getStreamFromFile</span>(String imageUri, Object extra) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throws</span> IOException {
        String filePath = Scheme.FILE.crop(imageUri);
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (isVideoFileUri(imageUri)) {
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> getVideoThumbnailStream(filePath);
        } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> {
            BufferedInputStream imageStream = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> BufferedInputStream(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> FileInputStream(filePath), BUFFER_SIZE);
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ContentLengthInputStream(imageStream, (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span>) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> File(filePath).length());
        }
    }

    <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@TargetApi</span>(Build.VERSION_CODES.FROYO)
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> InputStream <span class="hljs-title" style="box-sizing: border-box;">getVideoThumbnailStream</span>(String filePath) {
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (Build.VERSION.SDK_INT >= Build.VERSION_CODES.FROYO) {
            Bitmap bitmap = ThumbnailUtils.createVideoThumbnail(filePath, MediaStore.Images.Thumbnails.FULL_SCREEN_KIND);
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (bitmap != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>) {
                ByteArrayOutputStream bos = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ByteArrayOutputStream();
                bitmap.compress(CompressFormat.PNG, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, bos);
                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ByteArrayInputStream(bos.toByteArray());
            }
        }
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>;
    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li></ul>

来自ContentPorivder传入的Scheme为”content”的下载处理：

<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">protected</span> InputStream <span class="hljs-title" style="box-sizing: border-box;">getStreamFromContent</span>(String imageUri, Object extra) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throws</span> FileNotFoundException {
        ContentResolver res = context.getContentResolver();

        Uri uri = Uri.parse(imageUri);
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (isVideoContentUri(uri)) { <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// video thumbnail</span>
            Long origId = Long.valueOf(uri.getLastPathSegment());
            Bitmap bitmap = MediaStore.Video.Thumbnails
                    .getThumbnail(res, origId, MediaStore.Images.Thumbnails.MINI_KIND, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>);
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (bitmap != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>) {
                ByteArrayOutputStream bos = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ByteArrayOutputStream();
                bitmap.compress(CompressFormat.PNG, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, bos);
                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ByteArrayInputStream(bos.toByteArray());
            }
        } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (imageUri.startsWith(CONTENT_CONTACTS_URI_PREFIX)) { <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// contacts photo</span>
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> ContactsContract.Contacts.openContactPhotoInputStream(res, uri);
        }

        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> res.openInputStream(uri);
    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li></ul>

来自Assets和Drawable中传入的Scheme为”assets”和”drawable”的下载处理：

<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">protected</span> InputStream <span class="hljs-title" style="box-sizing: border-box;">getStreamFromAssets</span>(String imageUri, Object extra) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">throws</span> IOException {
        String filePath = Scheme.ASSETS.crop(imageUri);
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> context.getAssets().open(filePath);
    }
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">protected</span> InputStream <span class="hljs-title" style="box-sizing: border-box;">getStreamFromDrawable</span>(String imageUri, Object extra) {
        String drawableIdString = Scheme.DRAWABLE.crop(imageUri);
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> drawableId = Integer.parseInt(drawableIdString);
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> context.getResources().openRawResource(drawableId);
    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li></ul>

3、ReentrantLock和Synchronized
这两个的比较，我查阅了一下网上的文章，本想自己做一些理解和总结，看了一篇文章觉得剖析得非常好，偷懒直接贴上链接地址，如果您对此知识还不是完全熟悉，那么推荐您也可以看看。（http://www.ibm.com/developerworks/cn/java/j-jtp10264/index.html）

4、Collections.synchronizedMap类(线程安全)
此Map用于可能多线程共享使用的情况。源码如下，无非就是将自身作为一个互斥量，进行Map的各种操作时用synchronized关键字将其锁住，保证线程安全。

<code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <K,V> Map<K,V> <span class="hljs-title" style="box-sizing: border-box;">synchronizedMap</span>(Map<K,V> m) {
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> SynchronizedMap<>(m);
    }

    <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">/**
     * @serial include
     */</span>
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> SynchronizedMap<K,V>
        implements Map<K,V>, Serializable {
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> final <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">long</span> serialVersionUID = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1978198479659022715</span>L;

        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> final Map<K,V> m;     <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Backing Map</span>
        final Object      mutex;        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Object on which to synchronize</span>

        SynchronizedMap(Map<K,V> m) {
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.m = Objects.requireNonNull(m);
            mutex = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>;
        }

        SynchronizedMap(Map<K,V> m, Object mutex) {
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.m = m;
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.mutex = mutex;
        }

        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> <span class="hljs-title" style="box-sizing: border-box;">size</span>() {
            synchronized (mutex) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> m.size();}
        }
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> boolean <span class="hljs-title" style="box-sizing: border-box;">isEmpty</span>() {
            synchronized (mutex) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> m.isEmpty();}
        }
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> boolean <span class="hljs-title" style="box-sizing: border-box;">containsKey</span>(Object key) {
            synchronized (mutex) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> m.containsKey(key);}
        }
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> boolean <span class="hljs-title" style="box-sizing: border-box;">containsValue</span>(Object <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">value</span>) {
            synchronized (mutex) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> m.containsValue(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">value</span>);}
        }
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> V <span class="hljs-title" style="box-sizing: border-box;">get</span>(Object key) {
            synchronized (mutex) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> m.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">get</span>(key);}
        }

        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> V <span class="hljs-title" style="box-sizing: border-box;">put</span>(K key, V <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">value</span>) {
            synchronized (mutex) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> m.put(key, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">value</span>);}
        }
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> V <span class="hljs-title" style="box-sizing: border-box;">remove</span>(Object key) {
            synchronized (mutex) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> m.remove(key);}
        }
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">putAll</span>(Map<? extends K, ? extends V> map) {
            synchronized (mutex) {m.putAll(map);}
        }
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">clear</span>() {
            synchronized (mutex) {m.clear();}
        }

        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> transient Set<K> keySet;
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> transient Set<Map.Entry<K,V>> entrySet;
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> transient Collection<V> values;

        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> Set<K> <span class="hljs-title" style="box-sizing: border-box;">keySet</span>() {
            synchronized (mutex) {
                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (keySet==<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>)
                    keySet = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> SynchronizedSet<>(m.keySet(), mutex);
                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> keySet;
            }
        }

        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> Set<Map.Entry<K,V>> <span class="hljs-title" style="box-sizing: border-box;">entrySet</span>() {
            synchronized (mutex) {
                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (entrySet==<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>)
                    entrySet = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> SynchronizedSet<>(m.entrySet(), mutex);
                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> entrySet;
            }
        }

        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> Collection<V> <span class="hljs-title" style="box-sizing: border-box;">values</span>() {
            synchronized (mutex) {
                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (values==<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>)
                    values = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> SynchronizedCollection<>(m.values(), mutex);
                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> values;
            }
        }

        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> boolean <span class="hljs-title" style="box-sizing: border-box;">equals</span>(Object o) {
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span> == o)
                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>;
            synchronized (mutex) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> m.equals(o);}
        }
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> <span class="hljs-title" style="box-sizing: border-box;">hashCode</span>() {
            synchronized (mutex) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> m.hashCode();}
        }
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> String <span class="hljs-title" style="box-sizing: border-box;">toString</span>() {
            synchronized (mutex) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> m.toString();}
        }

        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Override default methods in Map</span>
        @Override
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> V <span class="hljs-title" style="box-sizing: border-box;">getOrDefault</span>(Object k, V defaultValue) {
            synchronized (mutex) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> m.getOrDefault(k, defaultValue);}
        }
        @Override
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">forEach</span>(BiConsumer<? super K, ? super V> action) {
            synchronized (mutex) {m.forEach(action);}
        }
        @Override
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">replaceAll</span>(BiFunction<? super K, ? super V, ? extends V> function) {
            synchronized (mutex) {m.replaceAll(function);}
        }
        @Override
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> V <span class="hljs-title" style="box-sizing: border-box;">putIfAbsent</span>(K key, V <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">value</span>) {
            synchronized (mutex) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> m.putIfAbsent(key, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">value</span>);}
        }
        @Override
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> boolean <span class="hljs-title" style="box-sizing: border-box;">remove</span>(Object key, Object <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">value</span>) {
            synchronized (mutex) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> m.remove(key, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">value</span>);}
        }
        @Override
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> boolean <span class="hljs-title" style="box-sizing: border-box;">replace</span>(K key, V oldValue, V newValue) {
            synchronized (mutex) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> m.replace(key, oldValue, newValue);}
        }
        @Override
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> V <span class="hljs-title" style="box-sizing: border-box;">replace</span>(K key, V <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">value</span>) {
            synchronized (mutex) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> m.replace(key, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">value</span>);}
        }
        @Override
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> V <span class="hljs-title" style="box-sizing: border-box;">computeIfAbsent</span>(K key,
                Function<? super K, ? extends V> mappingFunction) {
            synchronized (mutex) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> m.computeIfAbsent(key, mappingFunction);}
        }
        @Override
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> V <span class="hljs-title" style="box-sizing: border-box;">computeIfPresent</span>(K key,
                BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
            synchronized (mutex) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> m.computeIfPresent(key, remappingFunction);}
        }
        @Override
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> V <span class="hljs-title" style="box-sizing: border-box;">compute</span>(K key,
                BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
            synchronized (mutex) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> m.compute(key, remappingFunction);}
        }
        @Override
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> V <span class="hljs-title" style="box-sizing: border-box;">merge</span>(K key, V <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">value</span>,
                BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
            synchronized (mutex) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> m.merge(key, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">value</span>, remappingFunction);}
        }

        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">writeObject</span>(ObjectOutputStream s) throws IOException {
            synchronized (mutex) {s.defaultWriteObject();}
        }
    }</code><code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span style="color: rgb(85, 85, 85); font-family: 'microsoft yahei'; font-size: 14px; line-height: 35px;">转载于：优快云 胖虎 ， </span><a target=_blank href="http://blog.youkuaiyun.com/ljphhj" style="text-decoration: none; box-sizing: border-box; color: rgb(12, 137, 207); font-family: 'microsoft yahei'; font-size: 14px; line-height: 35px;">http://blog.youkuaiyun.com/ljphhj</a>
</code>