import java.io.*;
import java.util.*;

public class CircleBuff
{
   public CircleBuff( int n)
   {
      maxsize = n;
      pos = new int[n];
      invalidate();
   }
   
   public void add( int position)
   {
      pos[nfs] = position;
      nfs = (nfs+1)%maxsize;
      if (currentsize++>maxsize) currentsize = maxsize;
   }
   
   public int getSize()
   {
      return(currentsize);
   }
   
   public int get( int offset)
   {
      int posset = 0-offset;
      if (posset > currentsize)
         return(UNFILLED);
      return(pos[(nfs+(maxsize+offset))%maxsize]);
   }
   
   public void invalidate()
   {
      for (int i=0 ; i<maxsize ; ++i)
         pos[i] = UNFILLED;
      currentsize = 0;
      nfs = 0;
   }
   
   public String toString()
   {
      String s = "";
      for (int i=0 ; i<maxsize ; ++i)
         s += i+"["+pos[i]+"] ";
      return(s);
   }
   
   private int maxsize;
   private int currentsize;
   private int nfs; // next free slot
   private int[] pos;
   
   static final int UNFILLED = -65535;
   
   public static void main( String args[])
   {
      CircleBuff nt = new CircleBuff(3);
      nt.add(10);
      nt.add(20);
      nt.add(30);
      nt.add(40); // over-writes 10
      System.out.println(nt);
      System.out.println("-1["+nt.get(-1)+"], -2["+nt.get(-2)+"], -3["+nt.get(-3)+"], -4["+nt.get(-4)+"]");
   }
}