具有相同名称但签名不同的构造函数无法运行

Question

I have those 2 constructors:

public StockItem(Long id, String name, String desc, double price) {
    this.id = id;
    this.name = name;
    this.description = desc;
    this.price = price;
}

public StockItem(Long id, String name, String desc, double price, int quantity) {
    this.id = id;
    this.name = name;
    this.description = desc;
    this.price = price;
    this.quantity = quantity;
}

Doing this in another class:

StockItem item2 = new StockItem();
item2.setId(Long.parseLong(idField.getText()));
item2.setName(nameField.getText());
item2.setDescription(descField.getText());
item2.setPrice((double) Math.round(Double.parseDouble(priceField.getText()) * 10) / 10);
item2.setQuantity(Integer.parseInt(quantityField.getText()));
System.out.println(item2);

The output is:

id, name, desc, price

Why does it not take the quantity into the item2??? If I do:

System.out.println(Integer.parseInt(quantityField.getText()));

It DOES give me the quantity.

Could anyone tell me why it does not realize to use the second StockItem constructor. Tried it even after deleteing the first StockItem constructor.

Answer 1

For one you are not using either constructor you displayed in your question. You are creating a new object then setting the fields using setters. You may want to take a look at your setQuantity method of your class and see what it is doing. You don't use either constructor here.

Try something like this to initialize your object:

StockItem item2 = new StockItem(Long.parseLong(idField.getText()), nameField.getText(), descField.getText(), (double) Math.round(Double.parseDouble(priceField.getText()) * 10) / 10, Integer.parseInt(quantityField.getText()));

It will actually use your constructor.

Also look at your toString() method of your StockItem class. It is probably not printing quantity. You need to add quantity field to your toString() method output.

Answer 2

In your toString() method in the StockItem you have to include the quantity as well. For example:

public String toString() {
    return id + ", " + name + ", " + description + ", " + price + ", " + quantity;
}

This way when you do System.out.println(item2); , the toString() will be invoked with the quantity included in the result.

Answer 3

The constructor you're using it isn't in the ones you're showing here. Are you sure you're able to run that without making a new constructor with no Arguments? If I'm not wrong, you should use them like this. If you want to use the first constructor:

Long id = Long.parseLong(idField.getText());
String name = nameField.getText();
String desc = descField.getText();
double price = (double) Math.round(Double.parseDouble(priceField.getText());

StockItem stockItemUsingFirstConstructor = new StockItem(id, name, desc, price);

And if you want to use the second constructor:

Long id = Long.parseLong(idField.getText());
String name = nameField.getText();
String desc = descField.getText();
double price = (double) Math.round(Double.parseDouble(priceField.getText());
int quantity = Integer.parseInt(quantityField.getText());

StockItem stockItemUsingSecondConstructor = new StockItem(id, name, desc, price, quantity);

This is called overloading . :)

PS: Used variables to make it more clear. :)