Valid Parentheses.java

class Solution {
    public boolean isValid(String s) {
        
        Stack<Character> stack=new Stack<>();
    
        for( int i=0;i<s.length();i++)
        {
            char ch=s.charAt(i);
            
            if(ch=='(' || ch == '{' || ch == '[' )
            {
                stack.push(ch);
            }
            else
            {
                if(stack.isEmpty())
                {
                    return false;
                }
                else
                {
                    
                
                if(ch==')' && stack.peek()=='(')
                    stack.pop();
                else if(ch==']' && stack.peek()=='[')
                    stack.pop();
                else if(ch=='}' && stack.peek()=='{')
                    stack.pop();
                else
                    return false;
                    
                    
                } 
            }   
        }
        
        return stack.isEmpty();
    }
}```