Question

*JAVA*

Can somebody take a look at my current challenge?

I need to throw a different exception when

a)(b is entered. It should throw "Correct number of parenthesis but incorrect syntax"

The code is as follows.

Stack class:

public class ArrayStack<E> {

   private int top, size;
   private E arrS[];
   private static final int MAX_STACK_SIZE = 10;

   public ArrayStack() {
       this.arrS = (E[]) new Object[MAX_STACK_SIZE];
       this.top = size;
       this.size = 0;
   }

   public void push(E value) {
       if (isFull() == true) {
           throw new ArrayIndexOutOfBoundsException("Stack is Full");
       } else
           this.arrS[this.size++] = value;

   }

   public E pop() {
       if (isEmpty() == true) {
           throw new ArrayIndexOutOfBoundsException("Stack is Empty");
       }
       return this.arrS[--this.size];
   }

   public boolean isFull() {
       return (this.size == MAX_STACK_SIZE) ? true : false;

   }

   public boolean isEmpty() {
       return (this.size == 0) ? true : false;

   }

   public int length() {
       return this.size;
   }

   public E topValue() {
       if (isEmpty() == true) {
           throw new IllegalArgumentException();
       }
       return this.arrS[this.size - 1];
   }

   public void clear() {
       this.size = 0;

   }

   public String show() {

       StringBuilder sb = new StringBuilder();
       sb.append(" ");
       for (int i = 0; i < this.size; i++) {
           sb.append(this.arrS[i]);
           sb.append(" ");

       }
       sb.append("");
       return sb.toString();

   }

}

Main driver:

import java.util.Scanner;

public class a3main {

   public static void main(String[] args) {
       int count = 0;

       Scanner scan = new Scanner(System.in);

       do {
           System.out.println("Enter an algebraic or arithmetic expression: ");

           String arg = scan.nextLine();

           ArrayStack<Character> stack = new ArrayStack<Character>();
           boolean flag = true;
           for (int i = 0; i < arg.length(); i++) {
               count++;
               char current = arg.charAt(i);

               if (current == '{' || current == '[' || current == '(') {
                   try {
                       stack.push(current);
                   } catch (Exception e) {
                       System.out.println("Excessive parenthesis combinations" + "\n");
                       flag = false;
                       break;

                   }
               }

               if ((current == '}' || current == ')' || current == ']')) {
                   if (stack.isEmpty() == true) {
                       System.out.println(
                               "Encountered error on the right of the expression: Missing left parenthesis" + "\n");
                       flag = false;
                       break;
                   }
                   char last = stack.topValue();
                   if (current == '}' && last == '{' || current == ')' && last == '(' || current == ']' && last == '[')
                       stack.pop();
                   else {

                       flag = false;

                       System.out.println("Mismatch between right and left closing statements " + "\n");
                       break;
                   }
               }

           }
           if (flag) {
               if (stack.isEmpty() == true) {
                   System.out.println("Correct parenthesis combinations: match" + "\n");
               } else {
                   System.out.println(
                           "Encountered error on the left of the expression: Missing right parenthesis" + "\n");
               }
           }
       } while (count != 0);
   }
}

Answer 1

Hello,

Here is the code, I have put all my comments in the code. Also, I have enclosed the screenshot of result for your reference.

All the very best !!!

import java.util.Scanner;

public class a3main extends Exception{ // You need to extend Exception class to throw your own exception

    public a3main (String s){

        super(s); // Calling the constructor of Exception class
    }

    public static void main(String[] args) {
        int count = 0;

        Scanner scan = new Scanner(System.in);
        boolean exception = false; // I have a flag added to continue after the exception
        do {
            System.out.println("Enter an algebraic or arithmetic expression: ");

            String arg = scan.nextLine();

            ArrayStack<Character> stack = new ArrayStack<Character>();
            boolean flag = true;
            
            try{ // Introduced a try catch block to make sure expression doesn't contain )(, in case then throw the exception
                
                if (arg.contains(")(")){
                    throw new a3main("Correct number of parenthesis but incorrect syntax\n"); // Here is the text you are looking for
                }
                
            } catch (Exception e) { // Catch the exception thrown, set the exception flag to true 
                
                System.out.println(e.getMessage());
                exception = true;
            }
            if (exception==true){ // if exception, then flag exception is set and simply continue.
                count++;
                continue;
            }

            for (int i = 0; i < arg.length(); i++) { // Rest all is your code untouched
                count++;

                char current = arg.charAt(i);

                if (current == '{' || current == '[' || current == '(') {
                    try {
                        stack.push(current);
                    } catch (Exception e) {
                        System.out.println("Excessive parenthesis combinations" + "\n");
                        flag = false;
                        break;

                    }
                }

                if ((current == '}' || current == ')' || current == ']')) {
                    if (stack.isEmpty() == true) {
                        System.out.println(
                                "Encountered error on the right of the expression: Missing left parenthesis" + "\n");
                        flag = false;
                        break;
                    }
                    char last = stack.topValue();
                    if (current == '}' && last == '{' || current == ')' && last == '(' || current == ']' && last == '[')
                        stack.pop();
                    else {

                        flag = false;

                        System.out.println("Mismatch between right and left closing statements " + "\n");
                        break;
                    }
                }

            }
            if (flag) {
                if (stack.isEmpty() == true) {
                    System.out.println("Correct parenthesis combinations: match" + "\n");
                } else {
                    System.out.println(
                            "Encountered error on the left of the expression: Missing right parenthesis" + "\n");
                }
            }
        } while (count != 0);
    }
}