@Module
public class RandomInjectionModule {

    private static Blood blood;

    public RandomInjectionModule() {
    }

    @Provides
    static Blood provideBlood(){

        if(blood != null) {
            return blood;
        }

        Random rnd = new Random();
        int rndNumber = rnd.nextInt(3);

        switch (rndNumber){
            case 0: blood = new A_Blood(); break;
            case 1: blood = new B_Blood(); break;
            case 2: blood = new AB_Blood(); break;
            case 4: blood = new O_Blood(); break;
            default: blood = new A_Blood();
        }

        return blood;
    }
}