How to reverse a number in Java

public class Utils {

    public static long reverse(long num) {
        long sum = 0;
        while (num != 0) {
            long lastDigit = (num % 10);
            sum = (sum * 10) + lastDigit;
            num = num / 10;
        }
        return sum;
    }

}

import org.junit.Test;

import static org.hamcrest.Matchers.equalTo;
import static org.junit.Assert.*;

public class UtilsTest {

    @Test
    public void reverse() {
        assertThat(Utils.reverse(201), equalTo(102L));
        assertThat(Utils.reverse(100), equalTo(1L));
        assertThat(Utils.reverse(1), equalTo(1L));
        assertThat(Utils.reverse(1564654), equalTo(4564651L));
    }
}