What you will get from it

Once you understand how the JVM works, you usually can tell which way of programming will be the most efficient. Sometimes, you just want to tinker, though, and find out by the experience.

In those cases, though not really hard, it is quite a pain to have to implement the comparison solution, especially when the method is tightly related to its object, so I wrote some code I could easily reuse to compare several implementations of a method.

And now I am sharing it.

What you will get from it

When using the comparison algorithm and logger, you will obtain this kind of output:

o.k.c.c.ImplComparer - Beginning performance comparison for method <hello>, (3 check(s), 10000 iteration(s) per check
o.k.c.c.ImplComparisonLogger - +--------+--------------------+--------+
o.k.c.c.ImplComparisonLogger - | Method | Avg time (ms)      | Result |
o.k.c.c.ImplComparisonLogger - +--------+--------------------+--------+
o.k.c.c.ImplComparisonLogger - | hello  | 3.6887             |    REF |
o.k.c.c.ImplComparisonLogger - | hello1 | 2.7880666666666665 | == REF |
o.k.c.c.ImplComparisonLogger - | hello2 | 1.9368             | == REF |
o.k.c.c.ImplComparisonLogger - +--------+--------------------+--------+

The columns are the following:

1. Method: the name of the method being evaluated;
2. Avg time (ms): the average execution time during the verification, in milliseconds;
3. Result: a comparison of results:
   • REF: for the reference (first) result, either if results both point to the same sector or both are void or null;
   • == REF: for a result equal to the reference result (using the .equals(Object) method);
   • != REF: for a result not equal to the reference result (using the .equals(Object) method).

How to use it?

Create a test project

This is a suggestion of course, but it seems ill-advised to add the comparer as a dependency to your project: it is only a programming tool.

You should add the project containing the class you wish to test as a dependency to your project.

Adding the comparer to your dependencies

This project is not available on any Maven repository. You must therefore:

1. clone this project in your own workspace;
2. install it to your local repository using the mvn install command;

3. add it as a dependency to your project:

   <dependency>
     <groupId>org.keyboardplaying</groupId>
     <artifactId>java-implementation-comparer</artifactId>
     <version>1.0.0</version>
   </dependency>

Comparing and logging

Preparing variants

For instance, if I want to compare several implementations of the method public static String hello(String name), you will have to write methods with the exact same signature (return type, parameters) but adding a number at the end of the name of the method, e.g. public static String hello1(String name).

The algorithm will search all methods with the same signature and increment the suffix until no more variant is found.

Perform the comparison

I personally tend to create a TestClass and make a main which execute the comparison. Below is an example:

    public static void main(String[] args) throws NoSuchMethodException, IllegalAccessException,
            IllegalArgumentException {
        /* Prepare the comparer */
        ImplComparer cmp = new ImplComparer();
        /* Uncomment to override default settings */
        // cmp.setChecks(3);
        // cmp.setIterations(10000);

        List<ImplCheckResult> results = cmp.compareStatic(ToBeTested.class, "hello",
                new Class<?>[] { String.class }, new Object[] { "Chop" });
        /* Non-static method variant */
        // List<ImplCheckResult> results = cmp.compare(new ToBeTested(), "hello",
        // new Class<?>[] { String.class }, new Object[] { "Chop" });

        /* Print the result */
        ImplComparisonLogger logger = new ImplComparisonLogger();
        logger.log(results);
    }