如何使用来自另一个类的私有变量打印默认构造函数

Question

I want to print the default private bloodtype and rhfactor which is O+ and + I want to print it from another class which has the main method.

I've already tried creating new objects and printed them but still it says that I'm accessing a private variable. When you input something on the scanner it prints it but if you input none I want to print the constructor with private variables!

public class blooddata {

    private String bloodtype;
    private String rhFactor;

    blooddata(){
        bloodtype = "O";
        rhFactor = "+";
    }

    blooddata(String btx, String rhx){
        this.bloodtype = btx;
        this.rhFactor = rhx;
    }

    public String getblood (String bloodtype){
        return bloodtype;
    }

    public String getfactor (String rhFactor){
        return rhFactor;
    }

    public void setblood(String bloodtype){
        this.bloodtype = bloodtype;
    }

    public void setfactor(String factor){
        this.rhFactor = factor;
    }
}

here is the class that has main method

import java.util.Scanner;

public class Runblooddata {

    static Scanner sc = new Scanner(System.in);
    static String btx;
    static String rhx;

    public static void main(String[] args) {

        System.out.print("Enter blood type: ");
        btx = sc.nextLine();

        System.out.print("Enter rhFactor: ");
        rhx = sc.nextLine();

        if (btx.isEmpty() || rhx.isEmpty()){
           blooddata asd = new blooddata(); //this is where i am lost
        }else{   
            blooddata bd = new blooddata();
            bd.setblood(btx);
            bd.setfactor(rhx);

            System.out.println(bd.getblood(btx));
            System.out.println(bd.getfactor(rhx));
        }
    }
}

Answer 1

Getters aren't supposed to have parameters.

When you declare a method parameter named the same as a field, the parameter hides the field. You basically return the parameter you take.

6.4.1. Shadowing

A declaration d of a field or formal parameter named n shadows, throughout the scope of d, the declarations of any other variables named n that are in scope at the point where d occurs.

public String getBlood() {
    return bloodtype;
}

public String getFactor() {
    return rhFactor;
}

I will help you to simplify it a bit.

final class Example {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter blood type: ");
        String btx = sc.nextLine();

        System.out.print("Enter rhFactor: ");
        String rhx = sc.nextLine();

        BloodData data = btx.isEmpty() || rhx.isEmpty() ? 
                new BloodData() : 
                new BloodData(btx, rhx);

        System.out.println(data.getBloodType());
        System.out.println(data.getRhFactor());
    }
}

final class BloodData {

    private final String bloodType;
    private final String rhFactor;

    BloodData() {
        this("O", "+");
    }

    public BloodData(String bloodType, String rhFactor) {
        this.bloodType = bloodType;
        this.rhFactor = rhFactor;
    }

    public String getBloodType() {
        return bloodType;
    }

    public String getRhFactor() {
        return rhFactor;
    }
}

Answer 2

As Andrew has already explain the design issue what you have in your code, I'll guide you towards the solution what you are seeking for.

    blooddata bd = new blooddata();

    if (!btx.isEmpty() && !rhx.isEmpty()){

        bd.setblood(btx);
        bd.setfactor(rhx);
    }
    System.out.println(bd.getblood());
    System.out.println(bd.getfactor());