Commons Lang、BooleanUtils.toStringYesNo()

import org.apache.commons.lang.BooleanUtils;

public class C2009033100 {
    public static void main(String[] args) {
        System.out.println(BooleanUtils.toStringYesNo(true));
        System.out.println(BooleanUtils.toStringYesNo(false));
        System.out.println(BooleanUtils.toStringYesNo(new Boolean(true)));
        System.out.println(BooleanUtils.toStringYesNo(new Boolean(false)));
    }
}

で、

yes
no
yes
no