如何更改“ private static final”参数？

Question

I am new to java and object oriented programming and I have a question. There is a huge java code which has multiple packages and scrapbooks (each has several classes). It has many "private static final" parameters with their values. Now, I need to make those values variable which means I need to change the value of those parameters and each time, run the code to get the result. It wont be easy if I change the code each time and run the code. I want to give the numbers one time to the code (like list of numbers) and run the code for that. Any idea how to do that with least changes to the current code? For example define new class and give all variables in that class as array and with a for loop like K_value=K(i) and change the code from eg "private static final int k = 10" to "private static final int k= K_value". To make it clear lets assume:

private static final K= 5
private static final Q= -5
private static final M= 1

and K can be:5, 10, 15 Q can be -5, -10, -15, -20 and M can be 1, 2 and I want to run the code with all/partial combinations of above values. eg: 1) K=5, Q=-5, M=1 and 2) K=5, Q=-5, M=2 3) K=5, Q=-10, M=1 and so on.

Answer 1

I will answer your question in regards to the least amount of changes requirement. Any approach that is 'quick and dirty' will be marked with @@@ and I would urge you to not use them in a production scenario (eg just use them for one-off testing purposes or some old inherited non-critical code). I will express some general thoughts about the outlined scenario afterwards.

1. Read an environment variable (or system property) into the static final variables and start the program multiple times with a different value for its environment variable / system property: private static final int someConst = Integer.parseInt(System.getEnv("someConst")) @@@

2. Make the variable non final and change the value after every run of your suggested for loop method. Please note that this is extremely fragile/dangerous/error-prone as the variables may only read once at eg the application startup @@@

3. Rewrite the components that use the given constants to require the value as a constructor or function parameter. Depending on the applications size or how confident you feel in refactoring an unknown code base this could prove to be difficult. Consider using this approach if you have a well tested application

When reading your question I noticed that the outlined scenario seems like an algorithm/logic which should operate on input values instead of constants (you described they are not constant anymore). If possible the code should be restructured to reflect these new circumstances: make it instantiatable (add a constructor parameter) for different values or add a parameter to the affected functions/classes. All of the suggested fixes are just workarounds to modify as little code as possible. My advice: rewrite this if the usage scenario is for a production environment and use one of the outlined hacky workarounds if this is a one-off tutorial/testing/exploration.