package text.java;
import java.util.Arrays;
public class ArrayStack<T> implements ArrayStackADT<T> {
    private final static int DEFAULT_CAPACITY = 100;
    int top;
    private T[] stack;
    public ArrayStack(){
        this(DEFAULT_CAPACITY);
    }
    public ArrayStack(int initialCapacity){
        top = 0;
        stack = (T[])(new Object[initialCapacity]);
    }

    public void setTop(int top) {
        this.top = top;
    }

    public void push(T element){

        if(size() == stack.length){
            expandCapacity();
        }
        stack[top] = element;
        top++;
    }
    public T pop() {

        top--;
        T result = stack[top];
        stack[top] = null;
        return result;
    }
    public T peek()  {

        return stack[top - 1];
    }

    @Override
    public boolean isEmpty() {
        if(top == 0){
            return true;
        }
        if(stack[top-1]==null){
            return true;
        }
        else {
            return false;
        }
    }
    @Override
    public int size() {
        return top;
    }
    private void expandCapacity() {
        stack = Arrays.copyOf(stack,stack.length*2);
    }
    @Override
    public String toString(){
        return Arrays.toString(stack);
    }
}