RemoveConsecutiveDuplicatesStack

package removingconsecutiveduplicates2;

import java.util.ArrayDeque;
import java.util.Deque;
import java.util.Stack;

public class App {
    public static void main(String[] args) {
        String a = "aaabbbcccdddeeefff";
        System.out.println(removePair(a));
    }

    public static String removePair(String str) {

        Stack<Character> stack = new Stack<>();
        String output = "";
        String rev= "";
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < str.length(); i++) {

            if (stack.isEmpty() || stack.peek() != str.charAt(i)) {
                stack.push(str.charAt(i));

            } else {

                stack.pop();
            }
        }


        while (!stack.isEmpty()) {
            output += stack.peek();
            stack.pop();

        }
        for(int i = output.length()-1;i>=0;i--){
            rev += output.charAt(i);
        }


        return rev;
    }
}