Finding palindrome in array in Java

static ArrayList<String> arr = new ArrayList<>();
public static void palidrome() throws IOException {
InputStream fis = new FileInputStream("C://tmp/palidrome.txt");
InputStreamReader isr = new InputStreamReader(fis, Charset.forName("UTF-8"));
BufferedReader br = new BufferedReader(isr);
String line;
while ((line = br.readLine()) != null) arr.add(line);
for (int i=0; i<arr.size(); i++) {
if (!isPal(arr.get(i))) arr.set(i, "-1");
System.out.println(arr.get(i));
}
}
public static boolean isPal(String str) {
int i=0; int k = str.length()-1;
while (i<=k) {
if (str.charAt(i)==str.charAt(k) ) {
i++;
k--;
}
else return false;
}
return true;
}