JAVA - How to validate Parentheses Opening and Closing Order

How to validate the Parentheses are opening and closing in correct order

To validate the correct order of the parentheses the sequence of characters is required to be analyzed in a string value:

• First define all types of parentheses which needs to be validated in the input string like ( , ) , { , } , [, ]
• Maintain the input order of the predefined parenthesis types.
• Before closing a parentheses validate the opening status of same type of parentheses.

The below Java program helps us to validate the correct order parentheses

package com.errorConsole.string.validation;

import java.util.HashMap;
import java.util.Stack;

public class ParenthesesValidator {

	public static void main(String arg[]) {
		
		
		//Valid Parentheses String value
		String inputString = "loading [a {file} ] with ( 10 number ) data";
		
		boolean isValidInput = validateParenthesesOrder(inputString);
		
		System.out.println("\nValid Parentheses Order = " + inputString);
		System.out.println("\nIs Valid = " + isValidInput);

		System.out.println("\n======================================================================================== ");
		
		//Invalid Parentheses String value
		inputString = "loading [a {file}  with (10 number ] ) data";
		isValidInput = validateParenthesesOrder(inputString);
		
		System.out.println("\n\nInvalid Parentheses Order = " + inputString);
		System.out.println("\nIs Valid = " + isValidInput);
	}

	public static boolean validateParenthesesOrder(String inputString) {
		
		//Convert String to character array
		char[] charArray = inputString.toCharArray();
		
		//Create map with predefined parentheses types 
		HashMap<Character, Character> hashMap = new HashMap<Character, Character>();
		hashMap.put('(', ')');
		hashMap.put('[', ']');
		hashMap.put('{', '}');
		
		//Stack to maintain the order
		Stack<Character> characterStack = new Stack<Character>();
		
		for (Character c : charArray) {
			if (hashMap.keySet().contains(c)) {
				characterStack.push(c);
			} else if (hashMap.values().contains(c)) {
				if (!characterStack.isEmpty() && hashMap.get(characterStack.peek()) == c) {
					characterStack.pop();
				} else {
					return false;
				}
			}
		}
		
		return characterStack.isEmpty();
	}

}

The above program produces the below output where invalid parentheses order is marked in red colour