import java.util.*; public class ArithmeticExpressionEvaluation { public static void main(String[] args) { Scanner in = new Scanner(System.in); System.out.print("Enter the expression to evaluate it: "); String exp=in.nextLine(); System.out.println(exp); System.out.println("Result: " + calculate(exp)); } public static long calculate(String expression) { Stack operandStack = new Stack<>(); Stack operatorStack = new Stack<>(); if (!isValidExpression(expression)) { try { throw new InvalidExpression(""); } catch (InvalidExpression invalidExpression) { invalidExpression.printStackTrace(); } } int i = 0; String currentInteger = null; int Ne =0; while (i < expression.length()) { if (expression.charAt(i) >= '0' && expression.charAt(i) <= '9') { currentInteger = expression.charAt(i) + ""; i++; while (i != expression.length() && (expression.charAt(i) >= '0' && expression.charAt(i) <= '9')) { currentInteger = currentInteger + expression.charAt(i); i++; } if(Ne != 0){ currentInteger = "-" + currentInteger ; } operandStack.push(Long.parseLong(currentInteger)); Ne=0; } else { if (expression.charAt(i) == ')') { while (operatorStack.peek() != '(') { performArithmeticOperation(operandStack, operatorStack); } operatorStack.pop(); }else if (expression.charAt(i) == '-' && (i==0 || !Character.isDigit(expression.charAt(i-1)) ) && i+1 < expression.length() && (expression.charAt(i+1) >= '0' && expression.charAt(i+1) <= '9')){ Ne = -1; } else { Character currentOperator = expression.charAt(i); Character lastOperator = (operatorStack.isEmpty() ? null : operatorStack.peek()); if (lastOperator != null && checkPrecedence(currentOperator, lastOperator)) { performArithmeticOperation(operandStack, operatorStack); } operatorStack.push(expression.charAt(i)); } i++; } } while (!operatorStack.isEmpty()) { performArithmeticOperation(operandStack, operatorStack); } return operandStack.pop(); } public static void performArithmeticOperation(Stack operandStack, Stack operatorStack) { try { long value1 = operandStack.pop(); long value2 = operandStack.pop(); char operator = operatorStack.pop(); long intermediateResult = arithmeticOperation(value1, value2, operator); operandStack.push(intermediateResult); } catch (EmptyStackException e) { System.out.println("Not a valid expression to evaluate"); throw e; } } public static boolean checkPrecedence(Character operator1, Character operator2) { List precedenceList = new ArrayList<>(); precedenceList.add('('); precedenceList.add(')'); precedenceList.add('/'); precedenceList.add('*'); precedenceList.add('%'); precedenceList.add('+'); precedenceList.add('-'); if(operator2 == '(' ){ return false; } if (precedenceList.indexOf(operator1) > precedenceList.indexOf(operator2)) { return true; } else { return false; } } public static long arithmeticOperation(long value2, long value1, Character operator) { long result; switch (operator) { case '+': result = value1 + value2; break; case '-': result = value1 - value2; break; case '*': result = value1 * value2; break; case '/': result = value1 / value2; break; case '%': result = value1 % value2; break; default: result = value1 + value2; } return result; } public static boolean isValidExpression(String expression) { if ((!Character.isDigit(expression.charAt(0)) && !(expression.charAt(0) == '(') && !(expression.charAt(0) == '-')) || (!Character.isDigit(expression.charAt(expression.length() - 1)) && !(expression.charAt(expression.length() - 1) == ')'))) { return false; } HashSet validCharactersSet = new HashSet<>(); validCharactersSet.add('*'); validCharactersSet.add('+'); validCharactersSet.add('-'); validCharactersSet.add('/'); validCharactersSet.add('%'); validCharactersSet.add('('); validCharactersSet.add(')'); Stack validParenthesisCheck = new Stack<>(); for (int i = 0; i < expression.length(); i++) { if (!Character.isDigit(expression.charAt(i)) && !validCharactersSet.contains(expression.charAt(i))) { return false; } if (expression.charAt(i) == '(') { validParenthesisCheck.push(expression.charAt(i)); } if (expression.charAt(i) == ')') { if (validParenthesisCheck.isEmpty()) { return false; } validParenthesisCheck.pop(); } } if (validParenthesisCheck.isEmpty()) { return true; } else { return false; } } } class InvalidExpression extends Exception { public InvalidExpression(String s) { super(s); } }

expression evaluation