UTP Brackets Validation

import java.util.Scanner;
import java.util.LinkedList;

public class TestMain {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        Stack brackets = new Stack();
        String[] inputBrackets = in.nextLine().split("");
        //Lengkapi

        boolean cek = true;

        for(int i = 0; i < inputBrackets.length; i++) {
            char current = inputBrackets[i].charAt(0);
            switch (current) {
                case '(':
                case '{':
                case '[':
                    brackets.push(inputBrackets[i]);
                    break;
                case ')':
                    if(!brackets.pop().equals("("))
                        cek = false;
                    break;
                case '}':
                    if(!brackets.pop().equals("{"))
                        cek = false;
                    break;
                case ']':
                    if(!brackets.pop().equals("["))
                        cek = false;
                    break;
            }
            if (!cek) {
                break;
            }
        }
        System.out.println(brackets.isEmpty());
    }
}


class Stack {
    private final LinkedList<String> stringLinkedList;

    public Stack() {
        stringLinkedList = new LinkedList<>();
    }

    public boolean isEmpty() {
        return stringLinkedList.isEmpty();
    }

    public void push(String pushedString) {
        stringLinkedList.addFirst(pushedString);
    }

    public String pop() {
        return stringLinkedList.removeFirst();
    }

    public String peek() {
        return stringLinkedList.getFirst();
    }
}