For starter, put something actually descriptive in the subject line.
"Please help" doesn't tell us anything about the subject of your email.

Seconds, "help me with my program" is a bit of a vague question, try
being more specific.

I don't know what algorithm you were trying to use
So I wrote a program on Euclid's Algorithm
==== Code Start ====
/**
* @date Dec 22, 2006
* @author CK
* @copyright (c) http://www.gfour.net
*/
public class GCD {

    public int getGcdByEuclidAlgo(int a, int b) {
        //boolean flag = false;
        int remainder=2;
        int number=0;
        int divisor=0;
        int previousDivisor =0 ;
        //just swapping the numbers
        if (a<b){
            a=a+b;
            b=a-b;
            a=a-b;
        }

        if (a > b) {

            number=a;
            divisor=b;
            while (remainder >1) {
                previousDivisor = divisor;
                remainder = number % divisor;
                System.out.println(remainder);
                System.out.println(divisor);
                if (remainder > b) {
                    a = a % b;
                    remainder = a;

                }else {
                    number = b;
                    divisor = remainder;
                }

            }
        }
        if (remainder==1)
            return 1;
        return previousDivisor;
    }

    /**
    * @param args
    */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int num1 = 1002;
        int num2 = 24;
        System.out.println("GCD= " + (new GCD()).getGcdByEuclidAlgo(num1,
num2));
    }

}

==== Code End ====
Hope this helps.

Cheers,
Ck
http://www.gfour.net

[code snipped]

   Yes, we can probably help you. What are you having difficulty with?

   - Oliver

"Please help!" is an awful subject line. Can I suggest that next time
you try to put a brief description of the problem in the subject. For
example "simple recursive method for greatest common divisor"

To get the best out of newsgroups I find it is a good idea to clearly
state what your program did and what you actually expected it to do.

I'd include some comments explaining how the class should be used.

I'd put a comment here explaining the algorithm to be used. If it is a
classic maths algorithm you could give it's name or the person who
invented it.

You assign to n1 and n2 in your constructor but never use them. These
declarations could be removed without affecting your program's output.

If you are planning to use n1 and n2 in your methods, it is good
object-oriented practice to declare them as private.

I'm not convinced that 1 is a better default value than 0 or null.

You don't need to pass a and b to solve() since you already have n1 and
n2. You could write this as
    public void solve() {
        gcd = getGCD(n1, n2);
    }

Again, you don't need to pass a and b.
    public int getGCD() {
       if (n2 == 0)
       // etc

You don't need a comment like that.
Comments like the following are completely useless for me
        // assign 1 to a
        a = 1;
I find it useful for comments to explain WHY you are doing something.
Too many comments impede readability.

I imagine that if you made getGCD static, you could delete the above two
lines and replace the line below with
        System.out.println("Answer is " + GCDSolver.getGCD(x, y));

Your algorithm looks fishy, I'd try the following version of your code,
stare at the DEBUG output and try to think why.

/*
 * A library of many useful maths routines. Currently only GCD.
 */
public class MathRoutines {
    /*
     * Return the greatest common divisor of two integers.
     * 'int a = GCD(8, 12);' should assign 4 to a.
     * However, GCD has a bug!
     */
    static int GCD(int a, int b) {
        System.out.println("a=" + a + ", b=" + b); // DEBUG
        if (b == 0)
            return a;
        else
            return GCD(a, a % b);
    }

    /*
     * This main() is included for test purposes. It can be left
     * in place even if this class is used by another class
     * which has it's own main()
     */
    public static void main(String[] args) {
        // Test whether order of arguments matters, it shouldn't.
        System.out.println("The GCD of 8 and 12 is " + GCD(8, 12));
        System.out.println("The GCD of 12 and 8 is " + GCD(12, 8));
    }
}

I don't want to solve your class assignment for you, it's almost solved
any way. But I'll try to ask some question that might help you to the
finishing line. I am curious if you wrote that getGCD method all by
yourself, from an algorithm described in English,  or you copied it
from someone else's notebook. If latter, you might as well skip the
rest of this post because you will not be able make sense of it.

What returns the GCD? A class does not 'return' anything, it has
methods that return something.

Do you intend to hold on to the integers of which you want to calculate
GCD? That would be the reason to have them as members.

Likewise, you would have gcd as a member only if you want to hold on to
the gcd and return it at some point after calculating the gcd. Is that
what you are trying to do?

You assign the member variables in the constructor, almost. But these
two variables, n1 and n2 are never used by any of the methods! Why do
you need the member variables?

I say almost above because as written, this method is not a
constructor. Constructors do not have return types. How would you
change this so that it becomes constructor, if you decide that you do
need such a ctor?

The calculated gcd is not used by any other method. What is the
purpose?

This is method that works. It is called by the main method of
GCDMainProgram and returns the correct gcd. But it does not use any
member variables of the class! Such a method is typically declared
'static' (look up what it means).

I assume Console is some class that allows console io. But you will
have to 'import' it. Look up what that means.

Do you need to?

What does this method do for the rest of the code in this method?

You have two choices:

1. Accept the two integers of which you want to calculate the gcd in
constructor and provide another method that returns previously
calculated gcd. If you take this route, you have to ensure gcd has been
calculated before client asks for it. One way to do this is to
calculate it in the constructor itself, possibly by calling the solve
method. If not, can you ensure that without using one more variable?

2. Get rid of the constructor and provide the functionality in a single
method.

And here are two bonus questions:

1. Why is the first choice above more appropriate if you have need the
gcd of the same pairs repeatedly?

2. How would you generalize the above for finding GCD of more then 2
numbers?