http://www.sauronsoftware.it/projects/jave/download.php
以上是获取所需jar包 maven获取不到

例子：

File file = new File("http://nigualsizhuo.sanqifenshe.cn/1568602545078.amr")
            Encoder encoder = new Encoder();
            long ls = 0;
            MultimediaInfo m;
            try {
                m = encoder.getInfo(source);
                ls = m.getDuration()/1000;

            } catch (Exception e) {
                System.out.println("获取音频时长有误：" + e.getMessage());
            }
            return ls;

还有一个页面，那边比较全一点

https://blog.csdn.net/qq_34288630/article/details/85836152