/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
 
        String hexValue = "73657269616C6E6F80";
        String binValue = hexStringToBin(hexValue);
 
        System.out.println("binValue : " + binValue);
 
        int index = binValue.lastIndexOf(0x80);
 
        System.out.println("index : " + index);
    }
 
    public static String hexStringToBin(String s) {
        int len = s.length();
        byte[] data = new byte[len / 2];
 
        for (int i = 0; i < len; i += 2) {
            data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4) + Character.digit(s.charAt(i + 1), 16));
        }
 
        return new String(data);
    }
}

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