Чет не въеду.
package com.javarush.task.task18.task1822;/*Поиск данных внутри файла*/import java.io.*;
public class Solution {
private static String stw;
public static void main(String[] args) throws IOException {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
String fileName = reader.readLine();
reader.close();
FileInputStream inFile = new FileInputStream(fileName);
int i;
StringBuilder builder = new StringBuilder();
while (((i) = inFile.read()) != -1) {
builder.append((char) i);
stw = builder.toString();
}
if (stw.startsWith(args[0])) {
System.out.println(stw);
}
inFile.close();
}
}