public class Semaphore{
        private int i = 0;
        public synchronized void take(){
            i++;
            while(i > 1){
                try{
                    wait();
                } catch (Exception e){
                    errors++;
                }
            }
        }
        public synchronized void release(){
            i = 0;
            this.notify();
        }
    }
    public class Worker extends Thread{
        private Semaphore semaphore;
        private int count;
        public Worker(int c,Semaphore semaphore){
            count = (c == 1 ? 1 : 0);
            this.semaphore = semaphore;
        }
        public void write(Template template){
            try{
                Path path = Paths.get(filepath);
                byte[] bytes = Files.readAllBytes(path);
                ByteArrayInputStream in = new ByteArrayInputStream(bytes);
                ObjectInputStream is = new ObjectInputStream(in);
                ArrayList<Template> arrayList =(ArrayList<Template>) is.readObject();
                arrayList.add(template);
                ByteArrayOutputStream out = new ByteArrayOutputStream();
                ObjectOutputStream os = new ObjectOutputStream(out);
                os.writeObject(arrayList);
                Files.write(path,out.toByteArray());
            } catch (Exception e){
                System.out.println("Thread - " + (count % 2) + " : " + count);
                e.printStackTrace();
            } finally {
                semaphore.release();
            }
        }
        public void run(){
            while(count < arrayList.size()){
                semaphore.take();
                write(arrayList.get(count));
                count+=2;
            }
        }
    }