Потоки и семафоры в Java

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.RandomAccessFile;
import java.util.Random;
 
 
public class FileWork {
    private String filename;
    private int elementsCount;
 
public String getFilename() {
    return filename;
}
 
public void setFilename(String filename) {
    this.filename = filename;
}
 
public int getElementsCount() {
    return elementsCount;
}
 
public void setElementsCount(int elementsCount) {
    this.elementsCount = elementsCount;
}
 
public FileWork(String filename, int elementsCount) {
    super();
    this.filename = filename;
    this.elementsCount = elementsCount;
}
 
public static void main(String[] args) {
 
}
 
public RandomAccessFile fileWork(String filename, int count) throws NumberFormatException, IOException {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    RandomAccessFile file = new RandomAccessFile(new File(filename), "rw");
    byte[] b = new byte[count];
    System.out.println("Enter byte array in file: ");
    for (int i = 0; i < count; i++) {
        b[i] = Byte.parseByte(br.readLine());
    }
    file.write(b, 0, b.length);
    return file;
}
}