Eliminate Parentheses.java

package com.example;

import java.util.Stack;

public class Main {

    public static final char OPENING_PARENTHESES = '(';
    public static final char CLOSING_PARENTHESES = ')';

    public static void swap(char[] string, int i, int j) {
        char temp = string[i];
        string[i] = string[j];
        string[j] = temp;
    }

    /**
     * @param leftParentheses  Index of the left parentheses in the string
     * @param rightParentheses Index of the right parentheses in the string
     */
    public static void reverseStringInsideParentheses(char[] string, int leftParentheses, int rightParentheses) {
        int left = leftParentheses + 1;
        int right = rightParentheses - 1;

        while (left < right) {
            // Swap
            swap(string, left, right);
            left++;
            right--;
        }
    }


    // The actual solution
    public static String solve(String string) {
        char[] solution = string.toCharArray();
        int n = solution.length;
        
        // Store openings parentheses indexes
        Stack<Integer> openings = new Stack<>();
        
        for (int i = 0; i < n; i++) {
            char currentChar = solution[i];
            if (currentChar == OPENING_PARENTHESES) {
                openings.push(i);
            }
            if (currentChar == CLOSING_PARENTHESES) {
                if (openings.isEmpty())
                    throw new IllegalStateException("Unbalanced parentheses !!!");

                int leftPar = openings.pop();
                int rightPar = i;
                reverseStringInsideParentheses(solution, leftPar, rightPar);
            }
        }

        // remove all parentheses in the string
        return String.valueOf(solution).replaceAll("[()]", "");
    }


    public static void main(String[] args) {
        String TEST_CASE_1 = "I(love)you"; //Ievolyou
        String TEST_CASE_2 = "I(love(you))too"; //Iyouevoltoo
        String TEST_CASE_3 = "Java Pro(gr(am(me))r)s"; //Java Proramemrgs
        String TEST_CASE_4 = "(abcd)"; //dcba
        String TEST_CASE_5 = "(ed(et(oc))el)"; //leetcode

        System.out.println(solve(TEST_CASE_1));
        System.out.println(solve(TEST_CASE_2));
        System.out.println(solve(TEST_CASE_3));
        System.out.println(solve(TEST_CASE_4));
        System.out.println(solve(TEST_CASE_5));
    }
}