Retrieving a random item from ArrayList [duplicate

Question

This question already has an answer here:

• Randomly select an item from a list 2 answers

I'm learning Java and I'm having a problem with ArrayList and RandomGenerator.

I have an object called catalogue which has an array list of objects created from another class called item.

I need a method in catalogue which returns all the information on one of the itemobjects in the list.
The item needs to be selected at random.

import java.util.ArrayList;
import java.util.Random;

public class Catalogue
{
    private Random randomGenerator;
    private ArrayList<Item> catalogue;

    public Catalogue ()
    {
        catalogue = new ArrayList<Item>();  
    }

    public Item anyItem()
    {
        int index = randomGenerator.nextInt(catalogue.size());
        return catalogue.get(index);
        System.out.println("Managers choice this week" + anyItem + "our recommendation to you");
    }

When I try to compile I get an error pointing at the System.out.println line saying..

'cannot find symbol variable anyItem'

Answer 1

See https://gist.github.com/nathanosoares/6234e9b06608595e018ca56c7b3d5a57

public static void main(String[] args) {
    RandomList<String> set = new RandomList<>();

    set.add("a", 10);
    set.add("b", 10);
    set.add("c", 30);
    set.add("d", 300);

    set.forEach((t) -> {
        System.out.println(t.getChance());
    });

    HashMap<String, Integer> count = new HashMap<>();
    IntStream.range(0, 100).forEach((value) -> {
        String str = set.raffle();
        count.put(str, count.getOrDefault(str, 0) + 1);
    });

    count.entrySet().stream().forEach(entry -> {
        System.out.println(String.format("%s: %s", entry.getKey(), entry.getValue()));
    });
}

Output:

2.857142857142857

2.857142857142857

8.571428571428571

85.71428571428571

a: 2

b: 1

c: 9

d: 88

Answer 2

You must remove the system.out.println message from below the return, like this:

public Item anyItem()
{
    randomGenerator = new Random();
    int index = randomGenerator.nextInt(catalogue.size());
    Item it = catalogue.get(index);
    System.out.println("Managers choice this week" + it + "our recommendation to you");
    return it;
}

the return statement basically says the function will now end. anything included beyond the return statement that is also in scope of it will result in the behavior you experienced

Answer 3

anyItem has never been declared as a variable, so it makes sense that it causes an error. But more importantly, you have code after a return statement and this will cause an unreachable code error.

Answer 4

public static Item getRandomChestItem(List<Item> items) {
    return items.get(new Random().nextInt(items.size()));
}

Answer 5

Here you go, using Generics:

private <T> T getRandomItem(List<T> list)
{
    Random random = new Random();
    int listSize = list.size();
    int randomIndex = random.nextInt(listSize);
    return list.get(randomIndex);
}

Answer 6

As I can see the code
System.out.println("Managers choice this week" + anyItem + "our recommendation to you");
is unreachable.