Java Annotation for validating ISO country code in the given string

ValidCurrencyCode.java

import javax.validation.Constraint;
import javax.validation.Payload;
import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;

import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.PARAMETER;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

/**
 * Annotation to validate the ISO Currency code.
 *
 * @author Robin Raju
 */
@Target({FIELD, PARAMETER})
@Retention(RUNTIME)
@Constraint(validatedBy = ValidCurrencyCodeValidator.class)
@Documented
public @interface ValidCurrencyCode {
    String message() default "wrong iso code";

    Class<?>[] groups() default {};

    Class<? extends Payload>[] payload() default {};

    boolean optional() default false;
}

ValidCurrencyCodeValidator.java

import com.google.common.base.Strings;
import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;
import java.util.Currency;
import java.util.Set;

public class ValidCurrencyCodeValidator implements ConstraintValidator<ValidCurrencyCode, String> {

    private Boolean isOptional;

    @Override
    public void initialize(ValidCurrencyCode validCurrencyCode) {
        this.isOptional = validCurrencyCode.optional();
    }

    @Override
    public boolean isValid(String value, ConstraintValidatorContext constraintValidatorContext) {
        boolean containsIsoCode = false;

        Set<Currency> currencies = Currency.getAvailableCurrencies();
        try {
            containsIsoCode = currencies.contains(Currency.getInstance(value));
        }catch(IllegalArgumentException e){
        }
        return isOptional ? (containsIsoCode || (Strings.isNullOrEmpty(value))) : containsIsoCode;
    }
}