Get autobox class from type

Question

I know this question may seem silly because I could just do this manually. But I like to have all my options in one place (and one place only).

I want to set up the available options for a program (using commons-cli) by using the names of the fields in a dummy options class so that I can assign the values to an instance of that class.

The problem is that I can't figure out how to take the class object corresponding to a primitive type and retrieve the corresponding autobox class.

Here's the code I would like to have work (except that there's no such method getAutoboxClass)

public class PlayGame {
    private static final Options opts = new Options();

    static {
        Field[] allOpts = MCTSOptions.class.getFields();
        for (Field f : allOpts) {
            opts.addOption(new Option(f.getName(), f.getName(), !f.getType()
                    .equals(Boolean.TYPE), f.getName()));
        }
    }

    public static void main(String[] args) throws IOException, ParseException,
            IllegalArgumentException, IllegalAccessException,
            InvocationTargetException, SecurityException, NoSuchMethodException {
        BasicParser bp = new BasicParser();
        CommandLine cl = bp.parse(opts, args);
        String[] remainArgs = cl.getArgs();

        MCTSOptions params = new MCTSOptions();
        for (Field f : MCTSOptions.class.getFields()) {
            String name = f.getName();
                if (f.getType().equals(Boolean.TYPE)) {
                    f.set(params, true);
                } else if (f.getType().equals(String.class)) {
                    f.set(params, cl.getOptionValue(name));
                } else {
                    String value = cl.getOptionValue(name);
                    Method m = f.getType().getAutoboxClass()
                            .getMethod("valueOf", String.class);
                    f.set(params, m.invoke(null, value));
                }
            }
        }
        //...
    }
}

where MCTSOptions looks like:

public class MCTSOptions {
    public boolean searchOnSample = false;
    public double winOnlyMult = 0.5;
    public double firstExplorationConstant = 2;
    public double nextLearningRate = 0.1;
    public double nextExplorationConstant = 2;
    public boolean firstUsesSqrt = false;
    public boolean nextUsesSqrt = false;
    public long timeGiven = 5000L;
    public long seed = 1L;
}

(so right now it's only longs and doubles, but in the future I might add other types)

Answer 1

There is no built-in way to do it.

That's why, for example, Guava provides a helper method for this task. Internally it's implemented as a simple mapping between primitives and wrappers.

Answer 2

Why don't you just use the objects (Boolean, Long, etc) instead of the primitives?