Is it possible to remember state in Java functions?

Question

I'm trying to graduate from C to Java, largely skipping C++ in the process. Both for fun, and as a learning experience, I'm converting a C program I wrote almost 7 years ago to Java, which computes sunrise & sunset given one's latitude and longitude (downloadable as http://alumni.caltech.edu/~tfly/sun.zip ).
A technique I sometimes used in C programs was to have a "first_time" variable in a function. If that function was being executed for the "first time," it would know to perform this or that initialization of various variables. Such a variable would be declared as "static" within the function (it would retain its state from one function call to the next). Often, I would do this simply as a matter of efficiency- to avoid having to do the same calculation over and over again:
/* Return the angle swept out since the Perihelion passage, "days_elapsed" ago.
double orbit(days_elapsed)
double days_elapsed;
     double x, y, cos_rads, radians;
     static char first_time = 1;
     static char *eccentricity = "\r\nEccentricity = 0.12345678";
     static double ecc, ecc_const, sqrt_const;
     if (first_time)
          first_time = 0;
          ecc = (double) APHELION_DIST / (double) AU_DISTANCE - 1;
          sprintf(eccentricity, "\r\nEccentricity = %.8f", ecc);
          output(eccentricity);
          sqrt_const = sqrt(1 - pow(ecc, 2));
          ecc_const = 2 * PI / SIDEREAL_YEAR;
...An obvious work-around (kluge) in Java would be to have class variables first_time_x specific to each function x that might want to know whether or not it's being called for the first time since the program was started.
My question has more to do with philosophy and program design. Is this a significant flaw in Java, or am I simply using a feature of C that lets me take the easy way out of a fundamental design problem?

Answer 1

Java doesn't have a concept of C-style static variables. You are supposed to remember things like this in object data members. Rather than use a counting integer, use "boolean initialized = false;" and assign it to true in your method with:
if (initialized == false) {
initialized = true;
Look at it this way, in C you'll have a separate variable for each function, all with different names. All you are doing in Java is moving that variable to the next wider scope - object level instead of method level.
If your functions form some kind of logical hierarchy, you can place the boolean initializer in the base class along with a method to perform the if() check. Then the only thing that changes is the implementation of the function in the derived classes. If you do it right, the polymorphic features of Java will call the right methods for the respective objects and you won't have to worry about a thing.
You said you skipped C++, so if some of this OOP terminology is too foreign, drop me a line at [email protected] and we can discuss it at length and I can save on the phone bills :-)