Java Programming

Greetings,

I am trying to understand the purpose of this code

 private static double scale(double x, int n)
2363:   {
2364:    if (Configuration.DEBUG && abs(n) >= 2048)
2365:    throw new InternalError("Assertion failure");
2366:    if (x == 0 || x == Double.NEGATIVE_INFINITY
2367:   || ! (x < Double.POSITIVE_INFINITY) || n == 0)
2368:    return x;
2369:    long bits = Double.doubleToLongBits(x);
2370:    int exp = (int) (bits >> 52) & 0x7ff;
2371:    if (exp == 0) // Subnormal x.
2372:   {
2373:    x *= TWO_54;
2374:    exp = ((int) (Double.doubleToLongBits(x) >> 52) & 0x7ff) - 54;
2375:   }
2376:    exp += n;
2377:    if (exp > 0x7fe) // Overflow.
2378:    return Double.POSITIVE_INFINITY * x;
2379:    if (exp > 0) // Normal.
2380:    return Double.longBitsToDouble((bits & 0x800fffffffffffffL)
2381:   | ((long) exp << 52));
2382:    if (exp <= -54)
2383:    return 0 * x; // Underflow.
2384:    exp += 54; // Subnormal result.
2385:    x = Double.longBitsToDouble((bits & 0x800fffffffffffffL)
2386:   | ((long) exp << 52));
2387:    return x * (1 / TWO_54);
2388:   }

I do not understand what  Configuration.DEBUG is doing.  Simple example will be helpful. 

The above masterpiece comes from the following link:   http://developer.classpath.org/doc/java/lang/StrictMath-source.html

I am attempting it to translate it (configuration.debug as well) to c++ and possible use it  in other java applications.

Thanks in advance.

Adam