Java – how to operate on large numbers that cannot be stored in a variable

In Java, I want to be able to operate on very large integers (which cannot be stored for a long time). What should I do?

What is the best way to do well? Should I create my own data type with several long variables?

Example:

public class MyBigInteger{
    private long firstPart;
    private long secondPart;

   ...
}

public MyBigInteger add(long a,long b){
    MyBigInteger res;

    // WHAT CAN I DO HERE,I guess I Could do something with the >> << operators,but I've never used them!

    return res;
}

thank you!

Solution

import java.math.BigInteger;

import java.math.BigInteger;

public class BigIntegerTest {

    public BigInteger add(long a,long b){
        BigInteger big1 = new BigInteger(Long.toString(a));
        BigInteger big2 = new BigInteger(Long.toString(b));

        return big1.add(big2);
    }

    /**
     * @param args
     */
    public static void main(String[] args) {
        System.out.println(new BigIntegertest().add(22342342424323423L,234234234234234234L));
    }

}