随笔

class PartnerOfSomeoneWhoNeedOnePartner {
    private final String nameOfTheOneWhoNeedOnePartner;
    private final String nameOfThePartner;
    private static PartnerOfSomeoneWhoNeedOnePartner partner;

    private PartnerOfSomeoneWhoNeedOnePartner(String nameOfTheOneWhoNeedOnePartner, String nameOfThePartner) {
        this.nameOfTheOneWhoNeedOnePartner = nameOfTheOneWhoNeedOnePartner;
        this.nameOfThePartner = nameOfThePartner;
    }

    public static PartnerOfSomeoneWhoNeedOnePartner helpSomeOneWhoNeedOneParter(String nameOfTheOneWhoNeedOnePartner) {
        if (nameOfTheOneWhoNeedOnePartner == null) {
            return null;
        }
        if (partner == null || partner.nameOfTheOneWhoNeedOnePartner.equals(nameOfTheOneWhoNeedOnePartner)) {
            partner = new PartnerOfSomeoneWhoNeedOnePartner(nameOfTheOneWhoNeedOnePartner, null);
        } else if (partner.nameOfThePartner == null) {
            partner = new PartnerOfSomeoneWhoNeedOnePartner(nameOfTheOneWhoNeedOnePartner, partner.nameOfTheOneWhoNeedOnePartner);
        } else {
            partner = null;
        }
        return partner;
    }

    @Override
    public String toString() {
        if (nameOfThePartner == null) {
            return nameOfTheOneWhoNeedOnePartner + " is alone.";
        }
        return nameOfThePartner + " and " + nameOfTheOneWhoNeedOnePartner + " is not alone.";
    }

    public static void main(String[] args) {
        PartnerOfSomeoneWhoNeedOnePartner luRenJia = PartnerOfSomeoneWhoNeedOnePartner.helpSomeOneWhoNeedOneParter("路人甲");
        System.out.println(luRenJia);
        PartnerOfSomeoneWhoNeedOnePartner luRenYi = PartnerOfSomeoneWhoNeedOnePartner.helpSomeOneWhoNeedOneParter("路人乙");
        System.out.println(luRenYi);
    }
}