//
// simple bounded stack class for arbitrary objects
// used only for JUnit explanation ...
//

public class BoundedStack {

  private Object[] stack;
  private int tos = -1;

  public BoundedStack(int capacity) {
    stack = new Object[capacity];
  }

  public void push(Object o) {
    if (++tos < getCapacity())
      stack[tos] = o;
    else
      throw new RuntimeException("stack full");
  }

  public Object peek() {
    return (tos < 0) ? null : stack[tos]; 
  }

  public Object pop() {
    if (tos < 0) return null;
    else return stack[--tos];
  }

  public int getCapacity() {
    return (stack == null) ? 0 : stack.length;
  }
}