Need help with Split String to create a calculator

[Max347]

This is my first post, so hopefully I can give enough information. I am running windows xp, using jGrasp to write code. I need to make a calculator in which the user inputs 2 floating point numbers and an operation, with and output of the answer with the original equation. I think I need to use the split function, however I dont know what to do once it is split. Here is what I have so far-

import javax.swing.*;
import java.awt.*;
import java.util.*;
public class Calculator{
public static void main (String[] args){
String inputString = JOptionPane.sho wInputDialog("b lah blah");
String[] result = inputString.spl it("//s");
for (int x=0; x<result.length ; x++)
}
}

I'm new, if you can't tell, so im sorry if this is extremely elementary. In my mind, I would want to give each part of the string a name or letter, then use those for the rest of the code. I dont know if this is possible. Ex- input- "2 + 1" would give a=2 b=+ c=1, then I could go about using if statements to separate the operations (I need +-/* and % (remainder)). Thanks! Max

[Max347]

Also, ive found references to arrays, so maybe thats my solution? If someone has a guide?
Thanks

[r035198x]

Do it in small steps and satisfy yourself that the current step is correctly done before moving to the next step.
1.) Make sure you are getting the input correctly from the user. System.out.prin t it out to the console to test this.
2.) Make sure your splitting is working as expected. Print out each value in the array to test this.(Can use java.util.Array s.toString for this).
3.) Now you can proceed to do the calculation depending on what the second value in your array is.

[Max347]

Do it in small steps and satisfy yourself that the current step is correctly done before moving to the next step.
1.) Make sure you are getting the input correctly from the user. System.out.prin t it out to the console to test this.
2.) Make sure your splitting is working as expected. Print out each value in the array to test this.(Can use java.util.Array s.toString for this).
3.) Now you can proceed to do the calculation depending on what the second value in your array is.

My requirements limit me to the one output, would this be easier to tokenize, and make tokens? Thanks!

[r035198x]

My requirements limit me to the one output..

What do you mean? Surely you can use System.out.prin tln statements during your testing. You canthen remove them when you submit the final thing to whoever.

.., would this be easier to tokenize, and make tokens? Thanks!

That's what String.split is doing in your code. It's breaking the input into tokens.

[Max347]

Oh alright, I gotcha on the outputs. As for the splits, how do I actually use them? Will the result change throughout the code as I use it for different things? What im asking, is can I name them or something? Thanks

[r035198x]

Oh alright, I gotcha on the outputs. As for the splits, how do I actually use them? Will the result change throughout the code as I use it for different things? What im asking, is can I name them or something? Thanks

result is a String array. You can access its elements using
result[0] //first element
result[i]// (i+1)th element

[Max347]

result is a String array. You can access its elements using
result[0] //first element
result[i]// (i+1)th element

Alright cool, thats exactly what I was looking for.
Ok, I put in the String a = a, etc, however it says it is not a statement.

String a = result[0];
String b = result[1];
String c = result[2];
switch (b)
{
case +:
case -:
case /:
case *:

I know I need to fill in each possible case, but is it right? The complier is telling me I can't do the String a = result[x]; lines. Also, do I need anything around each operation? Thanks

Im sorry in advance is this stuff is really stupid, its my second week in the class and the book is unclear. Thanks!

[Max347]

Ok, ive been experimenting, and took out the whole String a, String b business, I guess they dont need to specifically be defined. I now still have the "illegal start of expression on the colons in my cases. Am I missing something? Thanks

[r035198x]

Ok, ive been experimenting, and took out the whole String a, String b business, I guess they dont need to specifically be defined. I now still have the "illegal start of expression on the colons in my cases. Am I missing something? Thanks

You can't switch on Strings.
If you want to use a switch then you need to change the result[1] value to a char(you can switch on chars). Otherwise use if-else statements.

P.S Use Sun's Java tutorial as your reference. You can even download the whole thing to your computer.

[Max347]

You can't switch on Strings.
If you want to use a switch then you need to change the result[1] value to a char(you can switch on chars). Otherwise use if-else statements.

P.S Use Sun's Java tutorial as your reference. You can even download the whole thing to your computer.

What about floats? how about this-
This is what ive got-

Float.parseFloa t(result[0]) = n1;
Float.parseFloa t(result[2]) = n2;
switch (1)
{
case '+':
JOptionPane.sho wMessageDialog( inputString + " = " + n1 + n2);


Will that output 2 + 1 = 3? (I cant run it yet) Thanks

[r035198x]

What about floats? how about this-
This is what ive got-

Float.parseFloa t(result[0]) = n1;
Float.parseFloa t(result[2]) = n2;
switch (1)
{
case '+':
JOptionPane.sho wMessageDialog( inputString + " = " + n1 + n2);


Will that output 2 + 1 = 3? (I cant run it yet) Thanks

You really do need to go through that tutorial.
You probably wanted to do
[CODE=java]float n1 = Float.parseFloa t(result[0]);
float n2 = Float.parseFloa t(result[2]);
char c = result[1].chatAt(0);
switch(c) {
....[/CODE]

[Max347]

Yeah, I know I do. Im downloading it right now (thanks for the link btw). Here's what I have-

import javax.swing.*;
import java.awt.*;
import java.util.*;
public class Calculator{
public static void main (String[] args) {
String inputString = JOptionPane.sho wInputDialog("I nput...etc etc");
String[] result = inputString.spl it("//s");
for (int x=0; x<result.length ; x++)
float n1 = Float.parseFloa t(result[0]);
float n2 = Float.parseFloa t(result[2]);
char c = result [1].chatAt(0);
switch (c)
{
case '+':
JOptionPane.sho wMessageDialog( inputString + " = " + n1 + n2);
break;
case '-':
JOptionPane.sho wMessageDialog( inputString + " = " + n1 - n2);
break;
case '/':
JOptionPane.sho wMessageDialog( inputString + " = " + n1 / n2);
break;
case '*':
JOptionPane.sho wMessageDialog( inputString + " = " + n1 * n2);
break;
case '%':
JOptionPane.sho wMessageDialog( inputString + " = " + n1 % n2);
break;
}
}
}

I really appreciate you taking the time to do this for me, a stranger. thanks, Max

[r035198x]

1.) Use code tags when posting code (like I did above).
2.) Don't just copy the code, try to understand it. (You probably didn't pick that I made a typo in charAt).
3.) What is the for loop for?
4.) There is no showMessageDial og method in JOptionpane which takes one string as argument.

[Max347]

1.) Use code tags when posting code (like I did above).
2.) Don't just copy the code, try to understand it. (You probably didn't pick that I made a typo in charAt).
3.) What is the for loop for?
4.) There is no showMessageDial og method in JOptionpane which takes one string as argument.

Ok, sorry about the code. I took out the loop. What if I just put one output on the bottom? null? When I compile this, it goes through now, asks me for my info, but then doesnt output. Here is what I have-

import javax.swing.*;
import java.awt.*;
import java.util.*;
public class Calculator{
public static void main (String[] args) {
String inputString = JOptionPane.showInputDialog("Input...etc etc");
String[] result = inputString.split("//s");

float n1 = Float.parseFloat(result[0]);
float n2 = Float.parseFloat(result[2]);
char c = result [1].chatAt(0);
switch (c)
{
case '+':
JOptionPane.showMessageDialog(null, inputString + " = " + n1 + n2);
break;
case '-':
JOptionPane.showMessageDialog(null, inputString + " = " + n1 - n2);
break;
case '/':
JOptionPane.showMessageDialog(null, inputString + " = " + n1 / n2);
break;
case '*':
JOptionPane.showMessageDialog(null, inputString + " = " + n1 * n2);
break;
case '%':
JOptionPane.showMessageDialog(null, inputString + " = " + n1 % n2);
break;
}
}
}