07-js正则验证文件后缀名

function test2() {
var t = document.getElementById('test').value;
var reg =/.txt$/;
if (reg.test(t)) {
alert("ok");
} else {
alert("not ok");
}
}

import java.util.regex.Pattern;

public class TestLastIndexOf {
public static void main(String[] args) {
String fileName = "asdf.jpg";
if (isTxtPrefix(fileName)) {
System.out.println("yes");
} else {
System.out.println("no");
}
}

public static boolean isTxtPrefix(String fileName) {
if (fileName.lastIndexOf(".", fileName.length()) != -1) {
String prefix = fileName.substring(fileName.lastIndexOf(".",
fileName.length()));
if (prefix.equalsIgnoreCase(".txt")) {
return true;
} else {
return false;
}
} else {
System.out.println("error");
}
return false;
}
}