java获取文件后缀名(正则表达式)+文件名

String fileName="asadas.jsp";
String reg = ".+(.JPEG|.jpeg|.JPG|.jpg|.png|.PNG)$";
Matcher matcher =Pattern.compile(reg).matcher(fileName);
System.out.println(matcher.find());

public String[] simpleFile (String file){
int sum = file.lastIndexOf(".");
return new String[]{
file.substring(0, sum),
file.substring(sum + 1)
};
}