Use arrays to implement stack

栈：先入后出(FILO-First In Last Out)的有序链表。top–bottom, pop–push。

//use arrays to implement stack
class ArrayStack {
    private int maxSize;    //size of stack
    private int[] stack;    //data
    private int top = -1;   //top of the stack, initiated as -1

    //constructor
    public ArrayStack(int maxSize) {
        this.maxSize = maxSize;
        this.stack = new int[maxSize];
    }

    public boolean isFull() {
        return top == maxSize - 1;
    }

    public boolean isEmpty() {
        return top == -1;
    }

    //push
    public void push(int value) {
        if (isFull()) {
            System.out.println("The stack has been full. Can't push new value in it.");
            return;
        }
        top++;
        stack[top] = value;
    }

    //pop
    public int pop() {
        if (isEmpty()) {
            throw new RuntimeException("The stack has been empty. Can't pop.");
        }

        int value = stack[top];
        top--;
        return value;
    }

    //iterate (from top to bottom)
    public void showStack() {
        if (isEmpty()) {
            System.out.println("The stack is empty.");
            return;
        }

        for (int i = top; i >= 0; i--) {
            System.out.println("stack[" + i + "] = " + stack[i]);
        }
    }
}