Question

Write a Java application that checks a string for correct parenthesization. The input comes from the keyboard and should (but might not) consist solely of the delmiters (, ), [, ], {, and } separated by whitespace.

The output of the program must include following:

• OK
• Opener/closer mismatch
• Missing closer
• Missing opener
• Unexpected symbol

The name of your class should be ParenChecker.

For example, if the input was:

( [ { } ] )

the program should produce the following output:

OK

and if the input was:

(

the program should produce the output:

Missing closer

etc...

Answer 1

Code:

import java.util.Scanner;
class ParenChecker{
   public static void main(String args[]){
       Scanner s=new Scanner(System.in);
       System.out.print("enter input:");       //reading input.
       String k=s.next();   
       int top=-1,i,c=0;
       char j;
       char a[]=new char[100];
       for(i=0;i<k.length();i++){
           j=k.charAt(i);
           if(j=='(' || j=='{' || j=='['){
               a[++top]=j;                   //push into the stack.
          
           }
           else if(top!=-1 && (j=='}' || j==']' || j==')' ) ){
               if(j==']' && a[top]=='[')
                   top=top-1;
               else if(j=='}' && a[top]=='{')
                   top=top-1;
               else if(j==')' && a[top]=='(')
                   top=top-1;
               else{
                   System.out.println("Opener/Closer mismatch");
                   c=1;
                   break;
               }

           }
           else{
               System.out.println("Unexpected symbol");        //if unexpected symbol occurs other than brackets.

               break;
          
           }

       }
       if(top==-1)
           System.out.println("OK");       //printing ok if parenthesis is correct.
       else if(top!=-1 && c!=1){
           j=k.charAt(0);
           if(j=='(' || j=='{' || j=='[')
               System.out.println("Missing Closer");     
           if(j==')' || j=='}' || j==']')
               System.out.println("Missing Opener");
       }   
   }
}

Output 1:

Output 2: