Java Program to check for Valid IMEI Number

18 February 2014

Java program to accept a fifteen digit number from the user and check whether it is a valid IMEI number or not.

Question:

The International Mobile Station Equipment Identity or IMEI is a number, usually unique, to identify mobile phones, as well as some satellite phones. It is usually found printed inside the battery compartment of the phone.

The IMEI number is used by a GSM network to identify valid devices and therefore can be used for stopping a stolen phone from accessing that network. The IMEI (15 decimal digits: 14 digits plus a check digit) includes information on the origin, model, and serial number of the device.

See: Java Program to find check digit of an IMEI Number

The IMEI is validated in three steps:

Starting from the right, double every other digit (e.g., 7 becomes 14).
Sum the digits (e.g., 14 → 1 + 4).
Check if the sum is divisible by 10.

For Example:

If input is IMEI = 490154203237518

Since, 60 is divisible by 10, hence the given IMEI number is Valid. Design a program to accept a fifteen digit number from the user and check whether it is a valid IMEI number or not. For an invalid input, display an appropriate message.

Programming Code:

Java

/**
* The class IMEI inputs a 15 digit number and checks whether it is a valid IMEI or not
* @author : www.guideforschool.com
* @Program Type : BlueJ Program - Java
*/

import java.util.Scanner;
class IMEI
{
    int sumDig(int n) // Function for finding and returning sum of digits of a number
    {
        int a = 0;
        while(n>0)
        {
            a = a + n%10;
            n = n/10;
        }
        return a;
    }
    
    public static void main(String args[])
    {
        IMEI ob = new IMEI();
        Scanner sc = new Scanner(System.in);
        
        System.out.print("Enter a 15 digit IMEI code : ");
        long n = sc.nextLong(); // 15 digits cannot be stored in 'int' data type
        
        String s = Long.toString(n); // Converting the number into String for finding length
        int l = s.length();
        
        if(l!=15) // If length is not 15 then IMEI is Invalid
            System.out.println("Output : Invalid Input");
        else
        {
            int d = 0, sum = 0;
            for(int i=15; i>=1; i--)
            {
                d = (int)(n%10);
                
                if(i%2 == 0)
                {
                    d = 2*d; // Doubling every alternate digit
                }

                sum = sum + ob.sumDig(d); // Finding sum of the digits
                
                n = n/10;
            }
            
            System.out.println("Output : Sum = "+sum);
            
            if(sum%10==0)
                System.out.println("Valid IMEI Code");
            else
                System.out.println("Invalid IMEI Code");
        }
    }
}

Output:

1. Enter a 15 digit IMEI code : 654122487458946 Output : Sum = 80 Valid IMEI Code

2. Enter a 15 digit IMEI code : 799273987135461 Output : Sum = 79 Invalid IMEI Code

3. Enter a 15 digit IMEI code : 79927398713 Output : Invalid Input