通过其他类构造函数在 main 方法中创建对象时访问对象属性

Question

I have 3 classes Test, Factory and TV - Factory is aimed to create TVs (classes are included below).

How can I access or manipulate properties of new TV, that was created in main method of Test Class (via TV class constructor invoked by Factory method in Test class).

public class TV {

    private int productionYear;
    private double price;

    public TV (int productionYear, double price){
        this.productionYear = productionYear;
        this.price = price;
    }

}

public class Factory {

    public static int numberOfTV = 0;


    public void produceTV(int a, double b){
        TV tv = new TV(a,b);
        numberOfTV++;
    }


    public void printItems(){
        System.out.println("Number of TVs is: " + numberOfTV);

    }
}

public class Test {

    public static void main(String[] args) {

        Factory tvFactory = new Factory();
        tvFactory.produceTV(2001, 399);
        tvFactory.printItems();

    }
}

Answer 1

public class TV {

    private int productionYear;
    private double price;

    public TV(int productionYear, double price) {
        this.productionYear = productionYear;
        this.price = price;
    }

    public int getProductionYear() {
        return productionYear;
    }

    public void setProductionYear(int productionYear) {
        this.productionYear = productionYear;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }
}

public class Factory {

    public static int numberOfTV = 0;


    public TV produceTV(int a, double b) {
        TV tv = new TV(a, b);
        numberOfTV++;
        return tv;
    }


    public void printItems() {
        System.out.println("Number of TVs is: " + numberOfTV);

    }
}

public class Test {

    public static void main(String[] args) {

        Factory tvFactory = new Factory();
        TV tv = tvFactory.produceTV(2001, 399);
        tvFactory.printItems();

        // Do manipulation with tv reference here 

    }
}

Answer 2

Your problem is that your Factory class produces TVs but never ships them anywhere.

In order to manipulate an object, you need a reference to it. Simply have the produceTV method return the TV that is produced.

public TV produceTV(int a, double b){
  numberOfTV++;
  return new TV(a,b);      
}

Right now you create a reference that is never used; most likely the compiler will eliminate the TV object creation.