java 获取某个URL的文件扩展名的方法（非精确，精确的扩展名应该使用服务器返回的MIME-TYPE）

    public static String getFileExtension(URL extUrl) {

        //URL: "http://photosaaaaa.net/photos-ak-snc1/v315/224/13/659629384/s659629384_752969_4472.jpg"

       // String filename = "";

        //PATH: /photos-ak-snc1/v315/224/13/659629384/s659629384_752969_4472.jpg

        String extension="";

        String path = extUrl.getPath();

        //Checks for both forward and/or backslash

        //NOTE:**While backslashes are not supported in URL's

        //most browsers will autoreplace them with forward slashes

        //So technically if you're parsing an html page you could run into

        //a backslash , so i'm accounting for them here;

        String[] pathContents = path.split("[\\\\/]");

        if(pathContents != null){

            int pathContentsLength = pathContents.length;

            //System.out.println("Path Contents Length: " + pathContentsLength);

//            for (int i = 0; i < pathContents.length; i++) {

//                System.out.println("Path " + i + ": " + pathContents[i]);

//            }

            //lastPart: s659629384_752969_4472.jpg

            String lastPart = pathContents[pathContentsLength-1];

            String[] lastPartContents = lastPart.split("\\.");

            if(lastPartContents != null && lastPartContents.length > 1){

                int lastPartContentLength = lastPartContents.length;

               // System.out.println("Last Part Length: " + lastPartContentLength);

                //filenames can contain . , so we assume everything before

                //the last . is the name, everything after the last . is the

                //extension

                String name = "";

                for (int i = 0; i < lastPartContentLength; i++) {

                   // System.out.println("Last Part " + i + ": "+ lastPartContents[i]);

                    if(i < (lastPartContents.length -1)){

                        name += lastPartContents[i] ;

                        if(i < (lastPartContentLength -2)){

                            name += ".";

                        }

                    }

                }

                extension = lastPartContents[lastPartContentLength -1];

               // filename = name + "." +extension;

               // System.out.println("Name: " + name);

               // System.out.println("Extension: " + extension);

               // System.out.println("Filename: " + filename);

            }

        }

        return extension;

    }