Random Writer Project! Just started this

Question

Hi guys I am asked to create a random writer class, below is part of my assignment sheet:
You are to implement a Java public class RandomWriterWithArrayList that provides a random writing application. Your class should have a public main method that constructs an instance with the following three arguments that are input from the user at the keyboard
1. A non-negative integer k
2. A non-negative integer length (the number of random characters to print).
3. The name of an input file that contains more than k characters.
Here is a sample dialog
File Name: ArtOfWar.txt
Seed Length: 6
Characters to print: 300
my code so far is:
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class RandomWriterWithArrayList{
     public static void main (String[] args){
     public class FileReader{ ===============>>> Illegal modifier for the local class FileReader; only abstract or final is permitted
          private String book = "";
          public FileReader(String s){
               File f;
               try{
                    f = new File(s);
               catch (FileNotFoundException fnfe){
                    return;
     Scanner j = new Scanner(f) ======>>>f cannot be resolved
     while (j.hasNextLine()){
          book+= j.nextLine() + "";
     Scanner keyboard = new Scanner(System.in);why does my file reader class won't work??

Answer 1

yeah, that's what I did too but I am using a for loop instead of that.
There's still one problem I am facing with and it has to do with the instruction fro m the assignment sheet below:
If your program ever gets into a situation in which there are no characters to choose from, which can happen if the only occurrence of the current seed is at the exact end of the source, your program should pick a new random seed and continue.
I handle this by writing this code, but somehow it still fails to satisfy the condition needed
if (set.size() == 0) {
                    for (int i = 0; i < k; i++) {
                         word += alphabet.charAt((int) (Math.random() * 26));
                         set.add(word);
                         word = "";
                         result += set.get(0);
               else
                    result += set.get((int) (Math.random() * set.size()));
               I use the random math method here because the instruction told me to pick a random number in the list.