For a given a string expression containing only round brackets or parentheses, check if they are balanced or not. Brackets are said to be balanced if the bracket which opens last, closes first. code example

Example 1: bracket balancing program in java

import java.util.Scanner;
import java.util.ArrayList;
public class BalanceBracket {
public static void main(String[] args) {
	Scanner sc = new Scanner(System.in);
	System.out.println("enter a string with '(', '{' or '['");
	String s = sc.nextLine();
	String y = isBalanced(s);
	System.out.println(y);
}
static String isBalanced(String s)
{
	String result = "NO";
	ArrayList<String> al = new ArrayList<String>();
	
	for(int i = 0; i < s.length(); i++)
	{
		if(s.charAt(i) == '(' || s.charAt(i) == '{' || s.charAt(i) == '[')
        {
			al.add(Character.toString(s.charAt(i)));
		}
		
		else if(s.charAt(i) == ')' || s.charAt(i) == '}' || s.charAt(i) == ']')
		{
			if(al.size() != 0 && al.get(al.size()-1).equals("(") && s.charAt(i) == ')')
			{
				al.remove(al.size()-1);
			}
			else if(al.size() != 0 && al.get(al.size()-1).equals("{") && s.charAt(i) == '}')
			{
				al.remove(al.size()-1);
			}
			else if(al.size() != 0 && al.get(al.size()-1).equals("[") && s.charAt(i) == ']')
			{
				al.remove(al.size()-1);
			}
			else
			{
				return result = "NO";
			}
		}
		
	}
	if(al.isEmpty() == true)
	{
		return result = "YES";
	}
	return result;
}
}

Example 2: bracket balance java

// for Java

class Parser{
    static HashMap<Character,Character> bracket_map = new HashMap<>();

    static {
        bracket_map.put(')', '(');
        bracket_map.put('}','{');
        bracket_map.put(']','[');
    }
    
    boolean isBalanced(String s){
            
        Stack<Character> stack = new Stack<>();
        char temp;
        for (int i = 0; i < s.length(); i++) {
            temp = s.charAt(i);
            if(temp == '{' || temp == '[' || temp == '('){
                stack.push(temp);
            }else {
                if(stack.isEmpty() || stack.peek() != bracket_map.get(temp)) return false;
                stack.pop();
            }
        }
        return stack.isEmpty();
    }
}