tropic cape
I want to return null if list is empty, but I want to return an item that has heaviest weight. I don't know how to set up the method to accept both return options. Any ideas?
public Item heaviestItem(){
if (items.size() == 0) {
heaviestItem = null;
} else {
for(Item item: items) {
if (item.getWeight() > heaviestItem.getWeight()) {
heaviestItem = item;
}
}
}
return heaviestItem;
}
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graceful bluff
I want to return null if list is empty, but I want to return an item that has he...
in theory the return type Item does allow null values to be returned. If you want to you can use Optional<Item> instead which just stresses that this item might be null and that the user who calles this functions needs to make sure that a valid value is returned
tropic cape
Well, this is MOOC challenge and it gives me an error when I submit.
graceful bluff
yeah because heaviest item doesn't have a type. It should be Item heaviestItem
tropic cape
Sorry if this is stupid questions, but isn't that what I set as a type in my method?
graceful bluff
no in the method declaration you just specify the return type. The compiler has no way of knowing which variable inside that method should be of type item
tropic cape
I did set in my code heaviestItem as a type of Item
graceful bluff
where ?
tropic cape
Suitcase class:
public class Suitcase {
private ArrayList<Item> items = new ArrayList<>();
private int maxWeight;
private int weight;
private Item heaviestItem;
public Suitcase(int maxWeight) {
this.maxWeight = maxWeight;
this.weight = 0;
}
public void addItem(Item item) {
if ((this.weight + item.getWeight()) < this.maxWeight) {
items.add(item);
weight = weight + item.getWeight();
}
}
public String toString() {
if (items.size() == 0) {
return "no items (" + this.weight + "kg)";
} else if (items.size() == 1) {
return items.size() + " item (" + this.weight + "kg)";
} else {
return items.size() + " items (" + this.weight + "kg)";
}
}
public void printItems(){
for(Item item: items) {
System.out.println(item.toString());
}
}
public int totalWeight(){
return this.weight;
}
public Item heaviestItem(){
if (items.size() == 0) {
heaviestItem = null;
} else {
for(Item item: items) {
if (item.getWeight() > heaviestItem.getWeight()) {
heaviestItem = item;
}
}
}
System.out.println(heaviestItem);
return heaviestItem;
}
}
I have Item and Main class as well
graceful bluff
oh yeah ok I lacked that information. Whats the error you are getting ?
tropic cape
This is the main class:
public class Main {
public static void main(String[] args) {
// You can use the main to test your classes!
Item book = new Item("Lord of the rings", 2);
Item phone = new Item("Nokia 3210", 1);
Item brick = new Item("Brick", 4);
Suitcase suitcase = new Suitcase(10);
suitcase.addItem(book);
suitcase.addItem(phone);
suitcase.addItem(brick);
Item heaviest = suitcase.heaviestItem();
System.out.println("Heaviest item: " + heaviest);
}
}
graceful bluff
in your if statement add item != null && ...
tropic cape
What if it is?
graceful bluff
then you cant compare the two
tropic cape
Task says to return null if there are no items in suitcase
graceful bluff
what is line 58 ?
tropic cape
public Item heaviestItem(){
if (items.size() == 0) {
heaviestItem = null;
} else {
for(Item item: items) {
//Line 58 below
if (item.getWeight() > heaviestItem.getWeight()) {
heaviestItem = item;
}
}
}
System.out.println(heaviestItem);
return heaviestItem;
}
yeah just to be sure rewrite the code so that heaviestItem is always null at the start and add the null check in line 58
tropic cape
You are good! That logic makes lots of sense. Thanks a lot @graceful bluff
graceful bluff
you're welcome 🙂