Valid Parentheses Question Solution in java Code: import java.util.*; class Test { public static void main(String[] args){ Scanner scn = new Scanner(System.in); String s = scn.next(); System.out.println(isValid(s)); } public static boolean isValid(String s) { Stack<Character> st = new Stack<>(); for(int i=0;i<s.length();i++){ char ch = s.charAt(i); if(ch=='('||ch=='['||ch=='{'){ st.push(ch); }else if(st.isEmpty()){ return false; }else { char top = st.pop(); if(ch==')'&&top!='('){ return false; } if(ch=='}'&&top!='{'){ return false; } if(ch==']'&&top!='['){ return false; } } } return st.isEmpty(); } }