类中有一个数值类型码,但他并不影响类的行为,以一个新的类替换数值类型码.

常量只是一个数值,并没有类型检验,是bug之源.改为使用类的地址值来替代;

public class Person {
//    public static final int O = BloodGroup.O.getCode();
//    public static final int A = BloodGroup.A.getCode();
//    public static final int B = BloodGroup.B.getCode();;
//    public static final int AB = BloodGroup.AB.getCode();;

//    private int bloodGroup;
    private BloodGroup mBloodGroup;


//    public Person(int bloodGroup) {
//        mBloodGroup = BloodGroup.code(bloodGroup);
////        this.bloodGroup = bloodGroup;
//    }

//    public int getBloodGroupCode() {
//        return mBloodGroup.getCode();
//    }

//    public void setBloodGroup(int bloodGroup) {
//        mBloodGroup = BloodGroup.code(bloodGroup);
////        this.bloodGroup = bloodGroup;
//    }

    public BloodGroup getBloodGroup() {
        return mBloodGroup;
    }

    public Person(BloodGroup bloodGroup) {
        mBloodGroup = bloodGroup;
    }

    public void setBloodGroup(BloodGroup bloodGroup) {
        mBloodGroup = bloodGroup;
    }


}



public class BloodGroup {
    public static final BloodGroup O = new BloodGroup(0);
    public static final BloodGroup A = new BloodGroup(1);
    public static final BloodGroup B = new BloodGroup(2);
    public static final BloodGroup AB = new BloodGroup(3);
    private static final BloodGroup[] values = {O, A, B, AB};

    private final int code;

    public BloodGroup(int code) {
        this.code = code;
    }

    private int getCode() {
        return code;
    }

    private static BloodGroup code(int arg) {
        return values[arg];
    }

    public static void main(String[] args) {
//        Person person = new Person(Person.A);
        Person thePerson = new Person(BloodGroup.A);

//        person.getBloodGroupCode();
        thePerson.getBloodGroup().getCode();

//        person.setBloodGroup(Person.AB);
        thePerson.setBloodGroup(BloodGroup.AB);

    }
}