Question

Write a method called isMatch that takes a string of parentheses and check if all parentheses match correctly. The parameter string might consist of other characters. Ignore other characters, just check the () {} [] public static boolean isMatch(String expressionLine); Use a JCF ArrayDeque or LinkedList as a stack to store all open or left parentheses.

Use following main method to check your method.

public static void main(String[] args)

{

String[] expression = new String[]{"{5*(x+2)+(y-1);}", "32*(20+(x[i]*3)-1", "((){([][])})", "({}((0))", "{([]})", "{}())", "{"};

for (String st: expression) System.out.println(st + " is " + isMatch(st));

}

Answer 1

Stack.java

import java.util.LinkedList;

public class Stack {

   private LinkedList<Character> list = new LinkedList<>();

   public void push(char ch) {

       list.add(ch);

   }

   public char pop() {
       if (list.isEmpty()) {
           System.out.println("Underflow error");
           return '\0';
       } else {

           int size = list.size();

           char ch = list.get(size - 1);
           list.remove(size - 1);
           return ch;
       }
   }

   public LinkedList<Character> getList() {
       return list;
   }

   public void setList(LinkedList<Character> list) {
       this.list = list;
   }
  
  

}

Paranthesis.java

public class Paranthesis {

   static boolean isMatch(String str) {

       char[] arr = str.toCharArray();

       Stack stack = new Stack();

       for (int i = 0; i < arr.length; i++) {

           if (arr[i] == '{' || arr[i] == '(' || arr[i] == '[')
               stack.push(arr[i]);
           //System.out.println(stack.getList().toString());

           if (arr[i] == '}' || arr[i] == ')' || arr[i] == ']') {

               if (stack.getList().isEmpty()) {
                   return false;
               }

               else {
                   char ch = stack.pop();
                   //System.out.println("Stack pop is " + ch);
                   //System.out.println("Array is " + arr[i]);

                   if (ch == '(' && arr[i] == ')')
                       continue;
                   else if (ch == '{' && arr[i] == '}')
                       continue;
                   else if (ch == '[' && arr[i] == ']')
                       continue;
                   else
                       return false;

               }
           }

       }

       if (stack.getList().isEmpty())
           return true;
       else {
           return false;
       }
   }

   public static void main(String[] args) {
       // TODO Auto-generated method stub

       String[] expression = new String[] { "{5*(x+2)+(y-1);}", "32*(20+(x[i]*3)-1", "((){([][])})", "({}((0))",
               "{([]})", "{}())", "{" };

       for (String string : expression)
           System.out.println(string + " is " + isMatch(string));

   }

}

Output

{5*(x+2)+(y-1);} is true
32*(20+(x[i]*3)-1 is false
((){([][])}) is true
({}((0)) is false
{([]}) is false
{}()) is false
{ is false

Feel free to ask any doubts, if you face any difficulty in understanding.

Please upvote the answer if you find it helpful