We will make a simple calculator using if-else as well as switch-case statement: Simple calculator using if-else in Java.
We will use the Scanner class to read user inputs such as operator, number 1, and number 2.
SIMPLE CONSOLE CALCULATOR IN JAVA HOW TO
Not case-sensitive.ĬustomParserException - simple class inherited from Exception to throw custom errors. This tutorial is useful for beginners to understand how to build a very simple calculator using Core Java. "seven minus three times four" becomes "7-3*4".
NaturalParser.java - class responsible for 'translating' equations from English words to their numeric and symbolic equivalents, e.g. Runs in a while loop, prompting for input in the console and outputs useful information.ĮxpressionEvaluator.java - class responsible for evaluating equation strings, such as "5*2/5+5-1". The project is divided into three main classes:ĬonsoleInterface.java - class responsible for the 'UI'. The application does not detect spelling errors and fails to provide a result.ĭividing by zero follows standard Java behaviour, equals infinity. The application does not have unit tests to ensure proper behaviour of each function. I did not implement a fix as I've already spent above the suggested time limit of four hours. "seven five times three" will actually give you seventy five times three, 75*3). LimitationsĪlthough technically not a limitation (perhaps even a feature), the program allows for whole numbers more than 10 as input if they are typed in succession (e.g. I have designed a simple console calculator as follows but i need to create a loop where I can re run the program: So that I wont need to run the program again and again and it can take the input from the user and run by itself. Subtraction was replaced with addition of negative integers. Essentially the long expression is split into parts by operator precedence (multiplication and division first, addition second). The approach taken for expression evaluation is detailed in the comments of the ExpressionEvaluator class.
The project took me around 5 hours to complete, the longest amount of time was spent brainstorming and researching a suitable solution for evaluating string expressions, such as "5 * 4 / 3 + 4 - 7" without the use of libraries and JavaScript interpreters. : This is part of an interview process, see the Specification.md file for the specification of this project. How to do that when typing in the console: java -jar calculator.jar 3 + 7 Immediately issued a response and did not require the program to run.
("add " +"multiply " +"subtract " + "divide ") VarArgsDemo - show 1.5 variable arguments. ("What type of operation would you like to perform on these numbers?") Output to standard output and standard error and input from standard input. Int division = 0, addition = 0, subtraction = 0, multiplication = 0 I think it has something to do with the array of String that I created and the if statement. Hey guys, welcome to the first tutorial of the series, in this lesson we will go over basic console commands and making a console calculator.ECLIPSE IDE: htt. It does not allow me to enter my choices in the console. Without directly giving me the answer can someone help me with this simple calculator that I am trying to write?Įverything seem to work well except for the very end when I ask the user to make a choice for add,subtract, multiply, or divide.
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