ArrayStack.java

public class ArrayStack {
  private int[] s;
  private int top;
  
  public ArrayStack(int capacity) {
    s = new int[capacity];
    top = 0;
  }
  
  public boolean empty() {
    return top = 0;
  }
  
  public void push(int x) {
    if (top == s.length)
      throw new StackOverFlowException();
    else {
      s[top] = x;
      top++;
    }
  }
  
  public int pop() {
    if (empty())
      throw new EmptyStackException();
    else {
      top--;
      return s[top];
    }
  }
  
  public int peek() {
    if (empty())
      throw new EmptyStackException();
  } else {
    return s[top] -1;
  }
}