Balanced paranthesis challenge

public static boolean isBalanced(String str, StacksUsingArrays stack) throws Exception {
for(int i = 0;i<=str.length()-1;i++)
{
if(str.charAt(i) == ‘{’ || str.charAt(i)==’(’ || str.charAt(i)==’[’)
{
stack.push(str.charAt(i));

		}
		else if(str.charAt(i) == '}' || str.charAt(i)=='}' || str.charAt(i)=='}')
		{
			if(stack.isEmpty())
			{
				return false;
			}
			if(str.charAt(i) == '}')
			{
				if(stack.top() == '{')
				{
					stack.pop();
				}
				else
				{
					return false;
				}
			}
			else if(str.charAt(i) == ')')
			{
				if(stack.top() == '(')
				{
					stack.pop();
				}
				else
				{
					return false;
				}
			}
			else if(str.charAt(i) == ']')
			{
				if(stack.top() == '[')
				{
					stack.pop();
				}
				else
				{
					return false;
				}
			}

		}
		else{
		//nothing
		}
	}
	if(stack.isEmpty())
	{
		return true;
	}
	else{
		return false;
	}
}

it is returning me no as an output
help ASAP

but when i submitted it pass all the testcase so my problem is solved thanku