Making a Simple Calculator with Java

[colinNeedsJavaHelp]

I am attempting to program a very basic calculator. The program simply needs to prompt the use to input the computation i.e. 2 * 5

The program needs to compute this and display the result as "The result is: 10"

I think my problem comes when I need to tell java to compute the users input. I do not know what function or method I need to use. If anyone can help I would appreciate it.

Thanks

This is what I have so far:

 import java.io.*; 
import java.util.*;
public class Calculator
{
public static void main(String[] args)
throws java.io.IOException
{
String I;
double Input;
double Result;
double Interest;
 
InputStreamReader isr = new InputStreamReader(System.in);
 
BufferedReader br = new BufferedReader(isr);
 
System.out.println("What do you want to compute? ");
I = br.readLine();
 
Interest = Double.parseDouble(I);
 
Result = Math(Interest);
 
System.out.println("The result is: " +Result);
}
}
 

[r035198x]

I am attempting to program a very basic calculator. The program simply needs to prompt the use to input the computation i.e. 2 * 5

The program needs to compute this and display the result as "The result is: 10"

I think my problem comes when I need to tell java to compute the users input. I do not know what function or method I need to use. If anyone can help I would appreciate it.

Thanks

This is what I have so far:

import java.io.*;
import java.util.*;
public class Calculator
{
public static void main(String[] args)
throws java.io.IOExcep tion
{
String I;
double Input;
double Result;
double Interest;

InputStreamRead er isr = new InputStreamRead er(System.in);

BufferedReader br = new BufferedReader( isr);

System.out.prin tln("What do you want to compute? ");
I = br.readLine();

Interest = Double.parseDou ble(I);

Result = Math(Interest);

System.out.prin tln("The result is: " +Result);
}
}

What operations do you want to be able to perform on your calculator? Just the * or other operations as well. The code you have written is not doing any multiplication so you can't expect it to give you the correct answer yet. And colin, next time you post code, please wrap it around code tags.

[colinNeedsJavaHelp]

I need it to perform addition, subtraction, multiplication, and division.

I think there is a math function that will just calculate whatever input, right? I just cannot find it in my book.

thx,
colin

[colinNeedsJavaHelp]

Actually I might need to use the if command i just feel stuck right now

[r035198x]

I need it to perform addition, subtraction, multiplication, and division.

I think there is a math function that will just calculate whatever input, right? I just cannot find it in my book.

thx,
colin

There is no math function which will just figure it out. That is the function that you want to write.

You will need to be able to split the input String into the operands and the operation first, then use a switch to select which operation to do. Do you think you can write code to split the input String into the operands and operations first?

[colinNeedsJavaHelp]

There is no math function which will just figure it out. That is the function that you want to write.

You will need to be able to split the input String into the operands and the operation first, then use a switch to select which operation to do. Do you think you can write code to split the input String into the operands and operations first?

I am not really sure how to do that. I would have to make it perfom seperate calculations based on what the user inputs. How would I do that? I am a very novice programmer.

[r035198x]

I am not really sure how to do that. I would have to make it perfom seperate calculations based on what the user inputs. How would I do that? I am a very novice programmer.

The operation to perform depends on the operator that has been supplied. If you don't manage to separate the operator from the operands you won't be able to finish this. Have a look at the methods of the String class and chose the methods you think will be required to split a String like "4+5" into three strings, "4", "+", and "5".

[DeMan]

And of course.... it all depends on how simple youmean by simple computation. If you always know two variable and an operand all is goos....if you need to be able to do (slightly) more complex things, look up "Reverse Polish Notation". If you can set up a stack (or two ) in RPN you can do more complex math (though still using the most basic operations)

[colinNeedsJavaHelp]

I found out I need to use the If command.

Here are my instructions
It only expects primitive arithmetic expressions involving two operands connected by one of the operators. +,-,*, /

It only expects non-negative numbers in the input

It assumes that all numbers are real numbers

It assumes that the operands and operators in the user-input expressions are separated by spaces. for example 20 - 15 instead of 20-15


I do not know what to do for the if statements

[Ganon11]

As r0 said, you should focus first on separating the input into the numbers and the operator.

For now, let's assume you have the user input. Both operators are in integer variables (call them num1 and num2), and the operator is held in a String variable (call it oper). If the user entered a + sign, then oper's contents are "+", and you want to add num1 and num2 for the result. You can use the .equals() method on oper to see if it equals "+", "-", "*", or "/". These will be your if...else branches.