Java Modify Listing 20.9 EvaluateExpression.java to add operators ^ for exponent

Question

Java

Modify Listing 20.9 EvaluateExpression.java to add
operators ^ for exponent and % for modulus. For example, 3 ^ 2 is 9 and 3 % 2
is 1. The ^ operator has the highest precedence and the % operator has the same
precedence as the * and / operators. Your program should prompt the user to
enter an expression.

USE THIS SAMPLE TO TEST YOUR PROGRAM PLEASE!:
Enter an expression: (5 * 2 ^ 3 + 2 * 3 % 2) * 4
(5 * 2 ^ 3 + 2 * 3 % 2) * 4 = 160

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20.9

-----------------------------------------------------------------------------

import java.util.Stack;

public class EvaluateExpression {
public static void main(String[] args) {
    // Check number of arguments passed
    if (args.length != 1) {
      System.out.println(
        "Usage: java EvaluateExpression "expression"");
      System.exit(1);
    }

    try {
      System.out.println(evaluateExpression(args[0]));
    }
    catch (Exception ex) {
      System.out.println("Wrong expression: " + args[0]);
    }
}

/** Evaluate an expression */
public static int evaluateExpression(String expression) {
    // Create operandStack to store operands
    Stack operandStack = new Stack<>();

    // Create operatorStack to store operators
    Stack operatorStack = new Stack<>();

    // Insert blanks around (, ), +, -, /, and *
    expression = insertBlanks(expression);

    // Extract operands and operators
    String[] tokens = expression.split(" ");

    // Phase 1: Scan tokens
    for (String token: tokens) {
      if (token.length() == 0) // Blank space
        continue; // Back to the while loop to extract the next token
      else if (token.charAt(0) == '+' || token.charAt(0) == '-') {
        // Process all +, -, *, / in the top of the operator stack
        while (!operatorStack.isEmpty() &&
          (operatorStack.peek() == '+' ||
           operatorStack.peek() == '-' ||
           operatorStack.peek() == '*' ||
           operatorStack.peek() == '/')) {
          processAnOperator(operandStack, operatorStack);
        }

        // Push the + or - operator into the operator stack
        operatorStack.push(token.charAt(0));
      }
      else if (token.charAt(0) == '*' || token.charAt(0) == '/') {
        // Process all *, / in the top of the operator stack
        while (!operatorStack.isEmpty() &&
          (operatorStack.peek() == '*' ||
          operatorStack.peek() == '/')) {
          processAnOperator(operandStack, operatorStack);
        }

        // Push the * or / operator into the operator stack
        operatorStack.push(token.charAt(0));
      }
      else if (token.trim().charAt(0) == '(') {
        operatorStack.push('('); // Push '(' to stack
      }
      else if (token.trim().charAt(0) == ')') {
        // Process all the operators in the stack until seeing '('
        while (operatorStack.peek() != '(') {
          processAnOperator(operandStack, operatorStack);
        }
      
        operatorStack.pop(); // Pop the '(' symbol from the stack
      }
      else { // An operand scanned
        // Push an operand to the stack
        operandStack.push(new Integer(token));
      }
    }

    // Phase 2: process all the remaining operators in the stack
    while (!operatorStack.isEmpty()) {
      processAnOperator(operandStack, operatorStack);
    }

    // Return the result
    return operandStack.pop();
}

/** Process one operator: Take an operator from operatorStack and
   * apply it on the operands in the operandStack */
public static void processAnOperator(
      Stack operandStack, Stack operatorStack) {
    char op = operatorStack.pop();
    int op1 = operandStack.pop();
    int op2 = operandStack.pop();
    if (op == '+')
      operandStack.push(op2 + op1);
    else if (op == '-')
      operandStack.push(op2 - op1);
    else if (op == '*')
      operandStack.push(op2 * op1);
    else if (op == '/')
      operandStack.push(op2 / op1);
}

public static String insertBlanks(String s) {
    String result = "";
  
    for (int i = 0; i < s.length(); i++) {
      if (s.charAt(i) == '(' || s.charAt(i) == ')' ||
          s.charAt(i) == '+' || s.charAt(i) == '-' ||
          s.charAt(i) == '*' || s.charAt(i) == '/')
        result += " " + s.charAt(i) + " ";
      else
        result += s.charAt(i);
    }
  
    return result;
}
}

Explanation / Answer

import java.util.Stack;

public class EvaluateExpression {

   public static void main(String[] args) {
       // Check number of arguments passed

       if (args.length != 1) {
           System.out.println("Usage: java EvaluateExpression "expression"");
           System.exit(1);
       }

       try {
          
          
           System.out.println(args[0] + " = " + evaluateExpression(args[0]));
       } catch (Exception ex) {
           System.out.println("Wrong expression: " + args[0]);
       }
       /*
       * String expression=" ( 5 * 2 ^ 3 + 2 * 3 % 2 ) * 4 "; try {
       * System.out.println(expression + " = " +
       * evaluateExpression(expression)); } catch (Exception ex) {
       * System.out.println("Wrong expression: " + expression); }
       */
   }

   /** Evaluate an expression */
   public static int evaluateExpression(String expression) {
       // Create operandStack to store operands
       Stack<Integer> operandStack = new Stack<>();

       // Create operatorStack to store operators
       Stack<Character> operatorStack = new Stack<>();

       // Insert blanks around (, ), +, -, /, and *
       expression = insertBlanks(expression);

       // Extract operands and operators
       String[] tokens = expression.split(" ");

       // Phase 1: Scan tokens
       for (String token : tokens) {
           if (token.length() == 0) // Blank space
               continue; // Back to the while loop to extract the next token
           else if (token.charAt(0) == '+' || token.charAt(0) == '-') {
               // Process all +, -, *, / in the top of the operator stack
               while (!operatorStack.isEmpty()
                       && (operatorStack.peek() == '+'
                               || operatorStack.peek() == '-'
                               || operatorStack.peek() == '*' || operatorStack
                               .peek() == '/')) {
                   processAnOperator(operandStack, operatorStack);
               }

               // Push the + or - operator into the operator stack
               operatorStack.push(token.charAt(0));
           } else if (token.charAt(0) == '*' || token.charAt(0) == '/'
                   || token.charAt(0) == '%') {
               // Process all *, / in the top of the operator stack
               while (!operatorStack.isEmpty()
                       && (operatorStack.peek() == '*'
                               || operatorStack.peek() == '/' || operatorStack
                               .peek() == '%')) {
                   processAnOperator(operandStack, operatorStack);
               }

               // Push the * or / operator into the operator stack
               operatorStack.push(token.charAt(0));
           } else if (token.charAt(0) == '^') {
               // Process all *, / in the top of the operator stack
               while (!operatorStack.isEmpty() && operatorStack.peek() == '^') {
                   processAnOperator(operandStack, operatorStack);
               }
               // Push the ^ operator into the operator stack
               operatorStack.push(token.charAt(0));
           } else if (token.trim().charAt(0) == '(') {
               operatorStack.push('('); // Push '(' to stack
           } else if (token.trim().charAt(0) == ')') {
               // Process all the operators in the stack until seeing '('
               while (operatorStack.peek() != '(') {
                   processAnOperator(operandStack, operatorStack);
               }

               operatorStack.pop(); // Pop the '(' symbol from the stack
           } else { // An operand scanned
               // Push an operand to the stack
               operandStack.push(new Integer(token));
           }
       }

       // Phase 2: process all the remaining operators in the stack
       while (!operatorStack.isEmpty()) {
           processAnOperator(operandStack, operatorStack);
       }

       // Return the result
       return operandStack.pop();
   }

   /**
   * Process one operator: Take an operator from operatorStack and apply it on
   * the operands in the operandStack
   */
   public static void processAnOperator(Stack<Integer> operandStack,
           Stack<Character> operatorStack) {
       char op = operatorStack.pop();
       int op1 = operandStack.pop();
       int op2 = operandStack.pop();
       if (op == '+')
           operandStack.push(op2 + op1);
       else if (op == '-')
           operandStack.push(op2 - op1);
       else if (op == '*')
           operandStack.push(op2 * op1);
       else if (op == '/')
           operandStack.push(op2 / op1);
       else if (op == '^')
           operandStack.push((int) Math.pow(op2, op1));
       else if (op == '%')
           operandStack.push(op2 % op1);
   }

   public static String insertBlanks(String s) {
       String result = "";

       for (int i = 0; i < s.length(); i++) {
           if (s.charAt(i) == '(' || s.charAt(i) == ')' || s.charAt(i) == '+'
                   || s.charAt(i) == '-' || s.charAt(i) == '*'
                   || s.charAt(i) == '/')
               result += " " + s.charAt(i) + " ";
           else
               result += s.charAt(i);
       }

       return result;
   }
}

OUTPUT : (SEND Expression as Command Line Argument)

( 5 * 2 ^ 3 + 2 * 3 % 2 ) * 4 = 160

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