Chapter 15, Problem 19PE

Program Plan Intro

Expression Calculator

Program plan:

ExpressionCalculator.java

• Create a class named “ExpressionCalculator”. Inside the class,
  • Define the “main ()” method.
    • Define the scanner input
    • Prompt the user to enter the expression.
    • Assign the expression
    • Define the stack required.
    • Loop that iterates for validating the characters in the expression.
    • Using if condition validate operator and operator and push into respective stacks.
    • Use condition to evaluate the precedence of the operator.
    • Use condition to validate the characters and their syntax.
    • Display the required error message.
  • Define the method “isOperator ()”
    • Return the character.
  • Define the method “error ()”
    • Display the error message and exit
  • Define the method “precedence ()”
    • Set the precedence for each operators and return the precedence.
  • Define the method “evaluateTop ()”
    • Use condition to validate the operator
    • Based on the operator calculate the value.
    • Return the resultant values.
    • Else return the appropriate messages.
    • Push the values into the stack after evaluation