Parenthesis/Brackets Matching using Stack algorithm

Question

For example if the parenthesis/brackets is matching in the following:

({}) (()){}() () 

and so on but if the parenthesis/brackets is not matching it should return false, eg:

{} ({}( ){}) (() 

and so on. Can you please check this code? Thanks in advance.

public static boolean isParenthesisMatch(String str) {     Stack<Character> stack = new Stack<Character>();      char c;     for(int i=0; i < str.length(); i++) {         c = str.charAt(i);          if(c == '{')             return false;          if(c == '(')             stack.push(c);          if(c == '{') {             stack.push(c);             if(c == '}')                 if(stack.empty())                     return false;                 else if(stack.peek() == '{')                     stack.pop();         }         else if(c == ')')             if(stack.empty())                 return false;             else if(stack.peek() == '(')                     stack.pop();                 else                     return false;         }         return stack.empty(); }  public static void main(String[] args) {             String str = "({})";     System.out.println(Weekly12.parenthesisOtherMatching(str));  } 

Answer 1

Your code has some confusion in its handling of the '{' and '}' characters. It should be entirely parallel to how you handle '(' and ')'.

This code, modified slightly from yours, seems to work properly:

public static boolean isParenthesisMatch(String str) {     if (str.charAt(0) == '{')         return false;      Stack<Character> stack = new Stack<Character>();      char c;     for(int i=0; i < str.length(); i++) {         c = str.charAt(i);          if(c == '(')             stack.push(c);         else if(c == '{')             stack.push(c);         else if(c == ')')             if(stack.empty())                 return false;             else if(stack.peek() == '(')                 stack.pop();             else                 return false;         else if(c == '}')             if(stack.empty())                 return false;             else if(stack.peek() == '{')                 stack.pop();             else                 return false;     }     return stack.empty(); } 

Answer 2

This code is easier to understand:

public static boolean CheckParentesis(String str) {     if (str.isEmpty())         return true;      Stack<Character> stack = new Stack<Character>();     for (int i = 0; i < str.length(); i++)     {         char current = str.charAt(i);         if (current == '{' || current == '(' || current == '[')         {             stack.push(current);         }           if (current == '}' || current == ')' || current == ']')         {             if (stack.isEmpty())                 return false;              char last = stack.peek();             if (current == '}' && last == '{' || current == ')' && last == '(' || current == ']' && last == '[')                 stack.pop();             else                  return false;         }      }      return stack.isEmpty(); }