Very confused!

Question about the task

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I have a couple questions: 1) I do not understand the part on how to populate the Arraylist. I do understand that we can't create instances of Money but what are we adding to this lis? 2) what is happening here? "Person paul = new Person("Paul"); for (Money money : paul.getAllMoney()) " Thanks for educating me in advance!

Expand the program's ability to manipulate currencies.

1. Create a private double field amount in the abstract Money class.
2. Create a public getter for the field amount (public double getAmount()) so you can access it outside the Money class.
3. In the separate files, create Euro, Ruble, and USD classes, which will be descendants of the Money class.
4. In the Euro, Ruble, and USD classes, implement the getCurrencyName method, which will return the abbreviated name of the currency (String) (EUR, RUB, USD).
5. In the Euro, Ruble, and USD classes, implement a public constructor that takes one argument and calls the constructor of the base class (super class) with this argument.
6. Populate the allMoney list with all possible currency objects in accordance with the task conditions and the functionality of the program.

Requirements:

The Money class must have a private double field amount.
The Money class must implement a public constructor with one double parameter, which sets the variable amount to the passed parameter.
The Money class must implement a public getAmount method that returns the value of the field amount.
The Euro, Ruble, and USD classes must be descendants of the Money class and be located in separate files.
The Euro, Ruble and USD classes must implement the getCurrencyName method.
The getCurrencyName method must return the abbreviated name of the corresponding currency (String).
The Euro, Ruble, and USD classes must implement a public constructor with one double parameter. This constructor must set the value of the Money class's field amount by calling the parent class's constructor with the same argument.

package com.codegym.task.task14.task1417; import java.util.ArrayList; import java.util.List; /* Currencies */ public class Solution { public static void main(String[] args) { Person paul = new Person("Paul"); for (Money money : paul.getAllMoney()) { System.out.println(paul.name + " has a stash of " + money.getAmount() + " " + money.getCurrencyName()); } } static class Person { public String name; Person(String name) { this.name = name; this.allMoney = new ArrayList<Money>(); //write your code here /*Money Euro = new Money(); Money Ruble = new Money(); Money USD = new Money(); Money is an abstract class and cannot be instantiated*/ // create new instances of different currencies allMoney.add(new Euro (5)); allMoney.add(new Ruble(4)); allMoney.add(new USD(3)); } private List<Money> allMoney; public List<Money> getAllMoney() { return allMoney; } } }

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Guadalupe Gagnon

Level 37 , Tampa, United States

27 March 2020, 17:24

useful

You can create instances of Money

Money test1 = new Euro();
Money test2 = new Ruble();
Money test3 = new USD();

All of these are perfectly acceptable instances of Money. #2 getAllMoney() in the Person class returns a List(Money). That means it can be used as its return value in the code calling the method. Same as:

List<Money> test = paul.getAllMoney()

String test = "this is only a test";
char[] testArray = test.toCharArray();

for(char x : testArray)
   System.out.println(x);

for(char x : test.toCharArray())
   System.out.println(x);

lines 3-4 and 6-7 are doing the same exact thing.

Liliane Top

Level 17 , Amsterdam, Netherlands

27 March 2020, 18:06

#1 clear how to create new instances . but how did you know you also had to add the value to the List? How did you know that the Object Money consist of a name and a value? #2 that is an excellent explanation => paul is an instance of a Person and we invoke the getAllMoney() method from the class Person by using an instance of that Person. Thanks! All clear now!!

Liliane Top

Level 17 , Amsterdam, Netherlands

27 March 2020, 18:08

By the way I see you're already at level 37. Does it get easier? Do you really now understands how it works and are you now able to do the hard tasks more easily?

Guadalupe Gagnon

Level 37 , Tampa, United States

27 March 2020, 18:31

useful

Codegym tasks stay challenging through all the levels because you are learning new stuff the entire way. While Java itself is only 50 keywords, what they have created with just those 50 words is quite immense. All objects consist of a variable name and and initialization value. You can't use the variables unless they have been initialized. As far as using a class as an object like this:

Money test = new Euro();

That is the whole concept of object orientated programming. You have been using this all over the place. Examples:

ArrayList<String> temp = new ArrayList<>();
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
Date today = new Date();

All of these have classes with constructors, methods, fields etc. As far as the list, the last condition says "Populate the allMoney list with all possible currency objects in accordance with the task conditions and the functionality of the program.". allMoney list is a List of Money objects. The only Money objects that you can create are Euro, Ruble, and USD.... those are what should be added.