Chapter 20, Problem 20.14PE

Program Plan Intro

Postfix notation

Program plan:

• Import the required packages into the program.
• In the Exercise20_14 class,
  • In the main() method,
    • Check length of the argument. If yes, display the error message.
    • Declare the variable.
    • The for loop executes until the length of arguments. If yes, evaluate the expression.
    • In try block, call evaluateExpression() method by passing the input expression.
    • In catch, block, catch the exception.
  • In the evaluateExpression() method.
    • Create an object for Stack.
    • Extract operands and operators.
    • The while loop executes until token to scan the expression. If yes,
      • Extract an expression.
      • Check whether the length of expression is equal to 0. If yes, continue the code.
      • Otherwise, check the expression. If yes, call processAnOperator() method.
      • Otherwise, Call push() method to push an operand into stack.
    • Return the result.
  • In the processAnOperator() method.
    • Check whether operator. If yes, perform the addition operation and push the result to stack.
    • Otherwise, check whether operator. If yes, perform the subtraction operation and push the result to stack.
    • Otherwise, check whether operator. If yes, perform the multiplication operation and push the result to stack.
    • Otherwise, check whether operator. If yes, perform the division operation and push the result to stack.