TestStack2.java

/**
 * C07 L15
 * 
 * Improved Stack class that uses the length array member.
 */
class Stack2 {
    private int stck[];
    private int tos;

    Stack2(int size) {
        stck = new int[size];
        tos = -1;
    }

    void push(int item) {
        if (tos == stck.length - 1) {
            System.out.println("Stack is full.");
        } else {
            stck[++tos] = item;
        }
    }

    int pop() {
        if (tos < 0) {
            System.out.println("Stack underflow.");

            return 0;
        } else {
            return stck[tos--];
        }
    }
}

public class TestStack2 {

    public static void main(String[] args) {
        Stack2 mystack1 = new Stack2(5);
        Stack2 mystack2 = new Stack2(8);

        for (int i = 0; i < 5; i++)
            mystack1.push(i);
        for (int i = 0; i < 8; i++)
            mystack2.push(i);

        System.out.println("Stack in mystack1:");
        for (int i = 0; i < 5; i++)
            System.out.println(mystack1.pop());

        System.out.println("Stack in mystack2:");
        for (int i = 0; i < 8; i++)
            System.out.println(mystack2.pop());
    }
}