Calculator in Java
1º Assigment for the course Algorithms and Data structures.
Assignment 1: Calculator for arithmetic expressions
The task is to implement a program that calculates the value of an arithmetic expression that is entered by the user. The user interface is irrelevant: it can be commandline, or a desktop graphical interface, or a web interface. The implementation of a fancy UI does not substitute for mistakes in implementing the main functionality. The expression consists of numbers (integers or floating point) and arithmetic operators (+, -, *, /, ^). The expressions are given in the infix notation. The program should correctly calculate the result and display it. It should also detect syntax errors in the expression if they exist.
This assignment is an exercise in using stacks, both for conversion of expressions from infix to postfix form, and for calculating the value of expressions from the postfix form.
How to run it?
Download the full project, compile it and execute UsingCalculator.java.
Type one number press Enter, type one operator press Enter and so on. Type e when finished and it will display the infix form, the postfix form and the solution.
If you want to calculate for example: 10 + 2 * 4.5
Type 10 press Enter, Type + press Enter, Type 2 press Enter, Type * press Enter, Type 4.5 press Enter, Type e press Enter.
Infix form: 10 + 2 * 4.5
Postfix form: 10 2 4.5 * +
The solution is: 19.0
It is also compatible with the use of multiple parenthesis, another example: 2 * ( 4.5 - 2.5 ) + 6
Infix form: 2 * ( 4.5 - 2.5 ) + 6
Postfix form: 2 4.5 2.5 - * 6 +
The solution is: 10.0
And it is secure against wrong input, bad sintaxis etc.... It gives valuable info too. A few wrong examples:
+ 2 - 2
ERROR -> Unknown input. Please type only numbers and valid operators: +-*/^()
( 2 4 + 5 )
ERROR -> Invalid sintaxis. The expression: ( 2 4 + 5 ) has no mathematical sense.
( 2 + 4.5) * 6 ) + 4
ERROR -> Invalid use of parenthesis.