import java.io.*;

class Finder { 

    private String line1, line2, line3;     
    private BufferedReader keyboard, inStream;

    public static void main(String [] args) {
        Finder aFind = new Finder();     
        aFind.doSearch(args[0]);
    }

    private void doSearch(String fileName) {
        keyboard = new BufferedReader(new InputStreamReader(System.in), 1);
        String wanted = prompt("Type string to find:");
        line1 = "";
        line2 = "";
        try {
            inStream = new BufferedReader(new 
                               FileReader(fileName));

            while ((line3 = inStream.readLine()) != null) {
                if (line2.indexOf(wanted) >= 0)
                    displayLine();

                // advance to the next group of 3
                line1 = line2;
                line2 = line3;
                // and get new line3 from file...
            }

            //check the last line
            line3 = "";                    //remove null eof value
            if (line2.indexOf(wanted) >= 0)
                displayLine();
            inStream.close();
        }

        catch (IOException e) {
            System.err.println("Error in Finder: "+ e.toString());
            System.exit(1);
        }
    } 

    private void displayLine() {
        System.out.println("<<------------  context:");
        System.out.println(line1);
        System.out.println(line2);
        System.out.println(line3);
        System.out.println("                      ------------->>"); 
        System.out.println("");      
    }

    private String prompt(String message) {
        String reply = "";
         try {
            System.out.print(message);
            System.out.flush();
            reply = keyboard.readLine();
        }
        catch (IOException e) {
            System.out.println("Keyboard input " + e.toString() );
            System.exit(2);
        }
        return reply;
    }

}