import java.text.Collator;
import java.text.ParseException;
import java.text.RuleBasedCollator;
import java.text.spi.CollatorProvider;
import java.util.Locale;

public class MyCollatorProvider extends CollatorProvider {

    private static final Locale EN_US_CASEINSENSITIVE =
            new Locale("en", "US", "caseinsensitive");

    private static final Locale EN_US_GREEK =
            new Locale("en", "US", "greek");

    @Override
    public Locale[] getAvailableLocales() {
        return new Locale[] {
            EN_US_CASEINSENSITIVE,
            EN_US_GREEK
        };
    }

    @Override
    public Collator getInstance(Locale locale) {
        if (locale.equals(EN_US_CASEINSENSITIVE)) {
            Collator c = Collator.getInstance(Locale.US);
            // Ignore tertiary differences (case differences)
            c.setStrength(Collator.SECONDARY);
            return c;
        } else if (locale.equals(EN_US_GREEK)) {
            StringBuilder rules = new StringBuilder();
            // alpha should go between a and b
            rules.append("< a,A < \u03b1 < b,B");
            // beta should go between b and c
            rules.append("& b,B < \u03b2 < c,C");
            // add more rules here ....
            try {
                return new RuleBasedCollator(rules.toString());
            } catch (ParseException pe) {
                throw new Error(pe);
            }
        } else {
            throw new IllegalArgumentException(locale.toString());
        }
    }
}