stack example java program using interface

IntStack.java

interface IntStack {

        void push(int item);

        int pop();

}

FixedStack.java

class FixedStack implements IntStack {

        private int stack[];

        private int tos;

        FixedStack(int size)

        {

        stack=new int[size];

        tos=-1;

        }

        public void push(int item)

        {

        if(tos==stack.length-1)

                System.out.println("stack is full");

        else

                stack[++tos]=item;

        }

        public int pop()

        {

        if(tos<0)

        {

                System.out.println("stack underflow");

                return 0;

        }

        else

                return stack[tos--];

        }

        public static void main(String args[]) {

                FixedStack mystack1=new FixedStack(5);

                FixedStack mystack2=new FixedStack(8);

                for(int i=0;i<6;i++) mystack1.push(i);

                for(int i=0;i<9;i++) mystack2.push(i);

                System.out.println("stack in mystack1");

                for(int i=0;i<6;i++)

                System.out.println(mystack1.pop());

                System.out.println("stack in mystack2");

                for(int i=0;i<9;i++)

                System.out.println(mystack2.pop());

        }

}