PostOfficeQueue

public class PostOfficeQueue {
    private int tot;
    int l[];

    public PostOfficeQueue(int n){
        tot=n;
        l=new int[n];
        for(int temp:l){
            temp=0;
        }
    }

    public synchronized void deskStart(int i){
        l[i]=1;
        tot--;
    }

    public synchronized void deskFinish(int i){
        l[i]=0;
        tot--;
        notifyAll();
    }

    public synchronized int getFreeDesk(){
        while(tot==0){
            try{
                wait();
            }catch(InterruptedException e){
                return -1;
            }
        }
        int j=-1;
        for(Integer temp:l){
            j++;
            if(temp==0)return j;
        }
        return j;
    }

}