Rather Basic Question

**ashl7** · March 3rd, 2013, 05:53 PM

Hi all, I'm new to Java programming(and programming itself) and was looking for a website such this, to get some help once in a while and find some answers to my questions...I read the forum's principles, won't ask u to write my programs at all lol, just need to make myself better.

anyway, for a start, I have a question about manipulating the numbers of a long int...like how do I choose to work with the second number from right of a 10 digits number?
I have arrays in mind...manipulating the numbers would have been easy if I choose each number go to one slot of my array ,but I don't like it this way, cuz when I run my program, it asks from the user to to put number 1, press enter, then put number 2, press enter and so on, as I wrote it here:

Scanner x = new Scanner(System.in);
 
		int num[] = new int[10];
 
			for( int counter=1; counter<num.length; counter++){
			num[counter] = x.nextInt();

I wanted the user to put the whole number in, and then I manipulate for example 4th digit of the number from left!

And also, needed to know how I can make it to accept exactly between 8-12 digits, nothing more or nothing less...

hope I'm not breaking any rules

, if I am, let me know!

**Zyrion** · March 3rd, 2013, 07:17 PM

You could use string manipulation and parse methods from the Wrapper class.

Wrapper Class

**Norm** · March 3rd, 2013, 07:57 PM

make it to accept exactly between 8-12 digits, nothing more or nothing less...

You can check if the number entered by the user is in the desired range and if not ask the user again for a number in the desired range. The code would be in a loop that wouldn't exit until the used entered a number in range.

**ashl7** · March 4th, 2013, 02:57 AM

You could use string manipulation and parse methods from the Wrapper class.

I guess what I actually need is a method that gets a long integer, and changes it into an array of integers :/
what Parse methods do is changing between strings and integers!

**Starstreak** · March 4th, 2013, 07:35 AM

Originally Posted by ashl7

Hi all, I'm new to Java programming(and programming itself) and was looking for a website such this, to get some help once in a while and find some answers to my questions...I read the forum's principles, won't ask u to write my programs at all lol, just need to make myself better.

anyway, for a start, I have a question about manipulating the numbers of a long int...like how do I choose to work with the second number from right of a 10 digits number?
I have arrays in mind...manipulating the numbers would have been easy if I choose each number go to one slot of my array ,but I don't like it this way, cuz when I run my program, it asks from the user to to put number 1, press enter, then put number 2, press enter and so on, as I wrote it here:

Scanner x = new Scanner(System.in);
 
		int num[] = new int[10];
 
			for( int counter=1; counter<num.length; counter++){
			num[counter] = x.nextInt();

I wanted the user to put the whole number in, and then I manipulate for example 4th digit of the number from left!

And also, needed to know how I can make it to accept exactly between 8-12 digits, nothing more or nothing less...

hope I'm not breaking any rules

, if I am, let me know!

Our numbering system uses base 10, so the second number from the right is the 100's column. Modulus divide the long integer by 100. {n%100, where n is the number} Then normal '/' divide by 10 to get that digit.
You then have the second to right digit without using Strings.

--- Update ---

Originally Posted by ashl7

I guess what I actually need is a method that gets a long integer, and changes it into an array of integers :/
what Parse methods do is changing between strings and integers!

If you really need to use Strings then convert the long to a String with the toString() method. From there you can create a character array with toCharArray() or split the string using split(). (The latter is a bit more tricky)

**Norm** · March 4th, 2013, 08:05 AM

check if the number entered by the user is in the desired range

The range of numbers I was talking about is 10000000 to 999999999999 ( lowest 8 digit number to highest 12 digit number)

**ashl7** · March 4th, 2013, 02:46 PM

Originally Posted by Starstreak

Our numbering system uses base 10, so the second number from the right is the 100's column. Modulus divide the long integer by 100. {n%100, where n is the number} Then normal '/' divide by 10 to get that digit.
You then have the second to right digit without using Strings.

--- Update ---

If you really need to use Strings then convert the long to a String with the toString() method. From there you can create a character array with toCharArray() or split the string using split(). (The latter is a bit more tricky)

That is great...thanks a lot, I don't think I even need an array anymore!!! . I'm not really good working with string methods...not that professional yet lol

but let's say I made a Char array...I want to add or subtract some of the numbers in this char array together, is that possible?! I mean those numbers are not integer anymore, they are characters!

--- Update ---

btw, how can I get a long int?

for an int is the method below, but I'm not sure I can use it for 16 digit integer
Scanner x = new Scanner(System.in)
int num = x.nextInt()

**Norm** · March 4th, 2013, 03:23 PM

how can I get a long int?

long is a primitive data type.
See the tutorial: Primitive Data Types (The Java™ Tutorials > Learning the Java Language > Language Basics)

**ashl7** · March 4th, 2013, 04:26 PM

so, it means we can't get a long int from the user?! and we can't use it as an object?
In C it was easy we just used scanf, but in java...

basically I wanted to the user put in a 15 digit number, now I'm not sure it would be easier working with arrays, or long int...cuz later on I want to work with each digit of that number!

**Norm** · March 4th, 2013, 04:37 PM

There is no long int. There is an int and there is a long. See the link in post#8
Also read the API doc for the Scanner class to see what its methods can read.

You can read a 15 digit number and you can create an object with it.

**ashl7** · March 4th, 2013, 05:36 PM

thanks, didn't know about API doc!!!
what's the difference of using nextLong(radix) and nextLong()?
it says in the description at the bottom that : radix - the radix used to interpret the token as an int value
so if i don't type radix in parenthesises, it will interpret the token as float or something else?!

--- Update ---

Originally Posted by Norm

The range of numbers I was talking about is 10000000 to 999999999999 ( lowest 8 digit number to highest 12 digit number)

when I use it in my loop it says : The literal 1000000000000 of type int is out of range!!!!!

**Norm** · March 4th, 2013, 05:42 PM

You need to learn how to use google to research terms you don't understand like radix.

Also reading the link I posted would help.

Here is another link for the API doc:
Java Platform SE 7

**ashl7** · March 5th, 2013, 09:02 PM

ok I used your help to do my program...I wrote it, but there is some problem in it that I can't figure out...
here is the summary of the problem:

let's say we have a 15 digits number ; we'll do the following to it:

Double every second digit from right to left. If doubling of a digit results in a two-digit number, add up the two digits to get a single-digit number.

Now add all single-digit numbers from above and show the result
-----------------------------------------

I made a small program to test it and see if it works
I assumed my number is 12523574
step one should be : 7*2=14>>5 , 3*2=6 , 5*2=10 >>1 , 1*2=2
step 2: 5+6+1+2 =14

now my code is below:

import java.util.*;
public class Test {
 
 
	public static void main(String[] args) {
 
 
		long cc=12523574;
 
		long i,j,u;
    	        long sum = 0;
 
    	for( long q = 100; q < 100000000; q*=100){
 
    		long p = q/10;
    		i = cc%q;
    		j = i/p;
    		u =2*j;
 
    		if(j>=10 && j<100){
    			long k= j%10;
    			long y= j/10;
    			long r= k + y;
 
    			sum+= r;
 
    		}
    		else if(j<10){
    			sum += u;
    		}
 
 
 
    	}
 
 
 
 
		System.out.println("\nsum " + sum);		
 
		}

but it keeps getting me 30!!! can u pls give me hint where my problem is? I'm out of ideas!

**Norm** · March 5th, 2013, 09:22 PM

Try printing out the results at each step and compare them to the results you get manually to see where the program is going wrong.

**ashl7** · March 5th, 2013, 10:02 PM

Got it, I'm so stupid and thanks much

it was in my if loop...I should have had variable u instead of j!

**Starstreak** · March 6th, 2013, 03:20 AM

Originally Posted by ashl7

I'm done with the program that I was working on,it was a part of writing a program to validate credit card numbers
now I'm off to start writing another program

) which mostly has to do with strings, which I kind of suck at!!

if I get a string from a user, how can I separate the digits and characters of it?! like if I want him to enter a name, and he enters something like jo7n, how can can I tell that's not a name?

I browsed javadoc, but it's a huge list of methods and classes, and for me, a beginner, I don't really know how to centralize my search in it...or where to look for specifically in all that information! any hint on where to start with?

Start a new thread for that. Meanwhile look in the API under either:
Matcher (Java Platform SE 7 )
or
String (Java Platform SE 7 )

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