Question

Program in Java

Create a stack class to store integers and implement following methods:

1- void push(int num): This method will push an integer to the top of the stack.

2- int pop(): This method will return the value stored in the top of the stack. If the stack is empty this method will return -1.

3- void display(): This method will display all numbers in the stack from top to bottom (First item displayed will be the top value).

4- Boolean isEmpty(): This method will check the stack and if it is empty, this will return true, otherwise false.

Answer 1

class Stack {
        final int MAX = 100;
        private int top;
        private int a[] = new int[MAX]; // Maximum size of Stack
        private int min;

        // constructer calls when the object is created
        Stack() {
                top = -1; // initialize top value -1
        }

        // this method is used to insert values into stack

        public void push(int x) {
                if (top >= (MAX - 1)) // here we check the condition if values are there are not
                {
                        System.out.println("Stack Overflow");
                } else {
                        a[++top] = x;
                }
        }

        // this method is used to delete top element
        public int pop() {
                if (top < 0) // here also we check the condition if values are there are not
                {
                        return -1;
                } else {
                        int x = a[top--];
                        return x;
                }
        }

        public boolean isEmpty() {
                return top < 0;
        }
        public void display() {
                for(int i=top-1;i>=0;i--)
                        System.out.print(a[i]+" ");
                System.out.println();
        }

}

public class TestIntegerStack {
        public static void main(String[] args) {
                Stack s = new Stack();
                System.out.println(s.isEmpty());
                s.push(10);
                s.push(20);
                s.push(30);
                s.push(40);
                s.push(50);
                s.push(60);
                s.display();
                s.pop();
                s.display();
                System.out.println(s.isEmpty());
        }
}

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