Thread: Concatenating Inputs, need help please!

import java.io.*;
public class Main {
public static void main(String[] args) throws IOException {
BufferedReader input = new BufferedReader (new InputStreamReader (System.in));
int num1, num2;
String shape, operation, pass;

System.out.print("Enter Operation: ");
operation = input.readLine();
System.out.print("Enter Number 1: ");
num1 = Integer.parseInt(input.readLine());
System.out.print("Enter Number 2: ");
num2 = Integer.parseInt(input.readLine());

OUTPUT
Enter Operation: +
Enter Number 1: 3
Enter Number 2: 5

* end of program *
But our professor wants us to have an output like this,

OUTPUT
Input: 3+5

He wants us to input 3 variables (int[3], String[+], int[5]) in one line. Is there a command that can return the cursor to the previous line so that after I enter "3", I can enter "+" next to it and not on the next line. Same goes with "5". Or is there other way to do this?

"3+5" there was supposed to be an input but they are equivalent to 3 variables which is (num1, operation, num3)

Let me put it this way. Let say I want to ADD 3 and 5. So the computer will ask me to enter/input my equation which is "3+5". Then, the computer will display the sum which is 8.

INPUT: 3+5
SUM: 8

So I'm asking if how could I do the "3+5" by using 3 different variables which is an integer, a String, and an integer that the user will input in one line only.

Maybe you want java.lang.Scanner - do you mean you type at the command prompt '3+5' all at once and your program reads the 3, then the +, then the 5?

@Sean4u
Yes! that's what I'm saying. Can you help me with the java.lang.Scanner because we are not using it in our class.

Can you help me with the java.lang.Scanner

Maybe, I think a lot of other forumers are more familiar with it than I am. Your first step is to read the API documentation for it to work out if it's right for your problem, what methods might work and then to actually give it a spin. You'd use a Scanner object in place of that BufferedReader. You could use BufferedReader (I would) to do this job, but then you'd have to explicitly extract the parts of your expression using something complicated like java.util.regex.Pattern

http://www.google.com/search?q=java%20Scanner
http://download.oracle.com/javase/1,...l/Scanner.html

I'm sorry but I don't really know how to use Scanner. I've tried some but I ended up the same with using BufferedReader.

Show us what you tried. A hint to get you going with Scanner without using java.util.regex.Pattern is to delimit your input. Put a space between each of your inputs like this: '3 + 5'. Then the Scanner methods which retrieve individual tokens can recognise where one token stops and another starts. If your professor wants you to be able to input expressions without whitespace, then things will get a little harder. If you can get your program working with Scanner and whitespace, you should be able to just 'upgrade' your input validation when you figure out how to do it. Do you think your professor want you to use Scanner, or does he want you to separate the terms of the expression without using any fancy classes from the API? You could ask him - it might be awful if you develop something fancy with Scanner, Pattern and Maps and then he says he wanted you to do it with character arrays.

Originally Posted by newbie

A simple program which reads in 1 line, then uses String.charAt(index) to get the first, second and third character

You're absolutely right ... if xdrechsler's professor has asked for a calculator program to add one-digit numbers. That's another thing xdrechsler could ask!

Got It!

import java.io.*;
import java.util.*;

public class NewClass {
public static void main(String args[]) throws IOException {
BufferedReader input = new BufferedReader (new InputStreamReader (System.in));
int num1 = 0, num2 = 0;
String operator = "", equation;

System.out.print("Enter Equation: ");
equation = input.readLine();

Scanner scan = new Scanner(equation);

while (scan.hasNext()) {
if (scan.hasNextInt()) {
if (num1 == 0) {
num1 = scan.nextInt();
System.out.println("NUM1: " + num1);
}
else {
num2 = scan.nextInt();
System.out.println("NUM2: " + num2);
}
}
else {
operator = scan.next();
System.out.println("OPERATOR: " + operator);
}
}
}
}

OUTPUT:

Enter Equation: 20 + 5
NUM1: 20
OPERATOR: +
NUM2: 5

Can you help me with the whitespace so that I can enter "20+5" instead of "20 + 5".

Good! Now do it newbie's way in post #12!

Do I have to change the entire program or I just add something to it with regards to newbie's post?

What I do when I'm learning programming languages (I never stop) is I get Program5 working first and then copy it to Porgram5UsingCharAt and just change the little bit that makes it different. That way I build up a collection of techniques for compare-and-contrast. All you need to do is to delete the code that uses Scanner and use String.charAt() instead. The code from chars to numbers can be a bit pervy - you'll want to subtract a base char from your 0-9 or convert to String and use Integer.parseInt ... or something. Give it a spin. When you've got that working, then you can do it all again to cope with '3+ 5' (unreliable whitespace).

Thanks! I'll give it a go later, I need to get some rest first, busy day for me.