An Experiment in Code Redundancy

When writing software we face a lot of uncertainty. Even when properly tested there is no guarantee that code is really bug-free. The best way to combat uncertainty is redundancy. Nature figured this out for us, this is why we have two eyes, two lungs, two kidneys, etc. We also use a lot of redundancy in software, for example in file storage. However, so far there’s not much redundancy in the code itself. Usually there is exactly one piece of code for any given task.

rdndc for Java is an experiment in code redundancy, which allows you to write multiple implementations of methods (and to some extent classes) that will be used based on some strategy. Redundant implementations of methods can be invoked probabilistically or as a fall back if an exception gets thrown.

Example

// different invokers use different strategies
Invoker invoker = new RandomInvoker(this);

 // public stub
public String format(String digits) {
    // the invoker chooses the implementation
    return (String) invoker.invoke("format", digits);
}

// mark method as redundant
@rdndc("format")
// private implementation
private String librarianFormat(String digits) {
    return String.format("%05d", Integer.parseInt(digits));
}

// mark method as redundant
@rdndc("format")
// another implementation
private String functionalFormat(String digits) {
    if (digits.length() >= 5) return digits;
    else return functionalFormat('0' + digits);
}

Acknowledgements

Inspired by and examples taken from The Narcissism of Small Code Differences.



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