java 8

import java.util.Scanner;

class Solution {

public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    char[] arr = new char[100];  
    while (sc.hasNext()) {
        String input = sc.next();
        boolean isBalanced = true;
        int top = -1;

        for (int i = 0; i < input.length(); i++) {
            char ch = input.charAt(i);

            if (ch == '(' || ch == '{' || ch == '[')
                arr[++top] = ch; 
            else if (ch == ')' || ch == '}' || ch == ']') {
                if (top == -1) {
                    isBalanced = false;
                    break;
                }
                else {
                    if (!isMatchingPair(arr[top--], ch)) {
                        isBalanced = false;
                        break;
                    }
                }
            }
        }
        if (top != -1) {
            isBalanced = false;
        }
        System.out.println(isBalanced ? "true" : "false");
    }
    sc.close();
}

static boolean isMatchingPair(char open, char close) {
    return (open == '(' && close == ')') ||
           (open == '{' && close == '}') ||
           (open == '[' && close == ']');
}

}