Implementing Stack using Array in Java

To understand more about Stack watch our video on Implementing Stack using Array in Java – click here

Q. What is a stack? 
Ans. Stack is a linear data structure implemented in Last in and First out or LIFO manner. Like for example a stack of plates, where insertion and deletion happens only at one end.

Q. What is overflow and underflow situation? Or What is difference between them?
Ans.

Q.  What are the two major stack operations?
Ans. The two operations performed on the stack are:

1. 1. Push: Adding (inserting) new element on to the stack.
   2. Pop: Removing (deleting) an element from the stack.

Q. list the different operations perform on the stack?
Ans.

1. 1. Push i.e., Insertion of element in the stack
   2. Pop i.e., Deletion of an element from the stack
   3. Peek i.e., viewing topmost element without removing it
   4. isEmpty() i.e., checks if the stack is empty.
   5. Display or view all the elements in the stack.

stack operation program .

import java.util.Scanner;
public class Stack
{
   String [] name;
   int cap;
   int top;
   boolean parenthesisChecker(String s)
   {
      for (int i = 0; i < s.length();i++) { char c = s.charAt(i); switch (c) { case '{': case '[': case '(': push(Character.toString(c)); break; case ')': String b = pop(); if (b.charAt(0) != '(') { System.out.println(b + " UnMatched ) "); return false; } break; case ']': b = pop(); if (b.charAt(0) != '[') { System.out.println(b + " UnMatched ] "); return false; } break; case '}': b = pop(); if (b.charAt(0) != '{') { System.out.println(b + " UnMatched } "); return false; } break; default: System.out.print("Ignore "+ c); } } return true; } Stack(int size) { cap = size; name = new String[cap]; top = -1; } Stack() { top = -1; cap = 100; name = new String[cap]; } void push (String s) { if (top+1 >= cap) 
      {
         System.out.println("Stack Overflow");
      }
      else 
      {
         top++;
         name[top] = s;
         System.out.println("push successful");
      }
   }
   String pop()
   {
      if (top < 0) 
      {
         System.out.println("Stack Underflow");
         return null;
      }
      else 
      {
         String s = name[top];
         top--;
         System.out.println("pop successful");
         return s;
      }
   }
   boolean isEmpty() 
   {
      return (top < 0);
   }
   void display() 
   {
      for (int i = 0; i <= top; i++) 
      {
         System.out.println(name[i]);
      }
   }
   String peek() 
   {
      if (top < 0) 
      {
         System.out.println("Stack Underflow");
         return null;
      }
      else 
      {
         String s = name[top];
         return s;
      }
   }
   public static void main(String[] args) 
   {
      Scanner input = new Scanner(System.in);
      int opt = 0;
      Node start = null;
      Stack nameStk = new Stack();
      do {
        System.out.println("Enter the option: \n1 Push \n2 Pop \n3 Display \n4 Peek \n5 isEmpty \n6 Quit");
        opt = input.nextInt();
        switch (opt ) {
          case 1:
             System.out.print("Enter name to add in stack");
             String data = input.next(); 
             nameStk.push(data);
             break;
          case 2:
             String s = nameStk.pop();
             System.out.println(s);
             break;
          case 3:
             nameStk.display();
             break;
          case 4:
             s = nameStk.peek();
             System.out.println(s);
             break;
          case 5:
             if(nameStk.isEmpty() == true)
                System.out.println("Stack Empty");
             else
                System.out.println("Stack Not Empty");
             break;
           case 7:
             System.out.print("Enter string to check");
             data = input.nextLine(); 
             if(nameStk.parenthesisChecker(data) == true)
                System.out.print("Matched");
             else
                System.out.print("UnMatched");
             break;
          }
       } while (opt != 6);
   }
}