I think my fault is line23.
String sub = s.substring(0,s.indexOf(" "));package com.codegym.task.task18.task1822;
/*
Finding data inside a file
*/
import java.io.*;
public class Solution {
public static void main(String[] args) throws IOException {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
String filename =reader.readLine();
FileInputStream fis = new FileInputStream(filename);
byte[] buffer = new byte[fis.available()];
fis.read(buffer);
String bufferstring = buffer.toString();
String[] list = bufferstring.split("/n");
fis.close();
for(int i = 0; i < list.length; i++ )
{
String s = list[i];
String sub = s.substring(0,s.indexOf(" "));
if(sub == args[0].toString())
{
System.out.println(s);
}
}
}
}