Code for answer on so question: http://stackoverflow.com/questions/7420900/registry-optimization-with-guice

Test.java

import java.util.HashMap;
import java.util.Map;
import java.util.Set;

import javax.inject.Inject;

import com.google.inject.Binder;
import com.google.inject.Guice;
import com.google.inject.Injector;
import com.google.inject.Module;
import com.google.inject.multibindings.Multibinder;

public class Test {
	public static void main(String[] args) {
		Injector injector = Guice.createInjector(new Module() {
			@Override
			public void configure(Binder binder) {
				@SuppressWarnings("rawtypes")
				Multibinder<Converter> converterBinder = Multibinder.newSetBinder(binder, Converter.class);
				converterBinder.addBinding().to(StringBooleanConverter.class);
				converterBinder.addBinding().to(BooleanStringConverter.class);
			}
		});
		ConverterRegistryImpl registry = injector.getInstance(ConverterRegistryImpl.class);
		System.out.println(registry.converterRegistry.size());

	}

	public static class ConverterRegistryImpl {

		private Map<Key, Converter<?, ?>> converterRegistry = new HashMap<Key, Converter<?, ?>>();

		@Inject
		public void setConverters(@SuppressWarnings("rawtypes") Set<Converter> converters) {
			for (Converter<?, ?> converter : converters) {
				register(converter.getFromClass(), converter.getToClass(), converter);
			}
		}

		private void register(Class<?> fromType, Class<?> toType, Converter<?, ?> converter) {
			converterRegistry.put(new Key(fromType, toType), converter);
		}

	}

	public static class Key {
		Class<?> first;
		Class<?> second;

		public Key(Class<?> first, Class<?> second) {
			this.first = first;
			this.second = second;
		}

	}

	private static class StringBooleanConverter implements Converter<String, Boolean> {

		@Override
		public Boolean convert(String input) {
			return Boolean.valueOf(input);
		}

		@Override
		public Class<String> getFromClass() {
			return String.class;
		}

		@Override
		public Class<Boolean> getToClass() {
			return Boolean.class;
		}

	}

	private static class BooleanStringConverter implements Converter<Boolean, String> {

		@Override
		public String convert(Boolean input) {
			return String.valueOf(input);
		}

		@Override
		public Class<Boolean> getFromClass() {
			return Boolean.class;
		}

		@Override
		public Class<String> getToClass() {
			return String.class;
		}
	}

	private interface Converter<E, T> {
		T convert(E input);

		Class<E> getFromClass();

		Class<T> getToClass();
	}
}