Creating a List in Java: Best Approaches

General Discussions
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1

How do you make a list in Java?

In Java, we create a Set using new HashSet(), but what is the correct way to make a list in Java? Are there multiple approaches, and which one is recommended for different use cases?

2

One of the most common and flexible ways to make a list in Java is by using ArrayList. It allows dynamic resizing and is generally the go-to choice for most scenarios.

import java.util.ArrayList;
import java.util.List;

public class Main {
    public static void main(String[] args) {
        List<String> cities = new ArrayList<>();
        cities.add("New York");
        cities.add("Los Angeles");
        cities.add("Chicago");

        System.out.println(cities);
    }
}

:white_check_mark: Why use this? :heavy_check_mark: Fast random access (O(1) for get() operations). :heavy_check_mark: Automatically resizes itself when needed. :heavy_check_mark: Ideal for storing ordered collections where retrieval speed is key.

:rotating_light: When to avoid? If you frequently add/remove elements from the middle of the list, LinkedList might be a better option.

3

That’s a great start! But if your use case involves frequent insertions or deletions, how to make a list in Java with LinkedList might be a smarter choice.

import java.util.LinkedList;
import java.util.List;

public class Main {
    public static void main(String[] args) {
        List<String> tasks = new LinkedList<>();
        tasks.add("Write code");
        tasks.add("Test software");
        tasks.add("Deploy application");

        System.out.println(tasks);
    }
}

:white_check_mark: Why use this? :heavy_check_mark: Fast insertions & deletions (O(1) when modifying the beginning/middle). :heavy_check_mark: Works well for queue-based operations (FIFO, LIFO). :heavy_check_mark: Avoids costly resizing operations that happen in ArrayList.

:rotating_light: When to avoid? If you need fast random access, ArrayList is far better since LinkedList requires traversing nodes to find an element.

4

Both ArrayList and LinkedList are great, but what if you don’t want to modify the list at all? In that case, how to make a list in Java using List.of() is the perfect solution for immutable collections.

import java.util.List;

public class Main {
    public static void main(String[] args) {
        List<String> colors = List.of("Red", "Green", "Blue");

        System.out.println(colors);
    }
}

:white_check_mark: Why use this? :heavy_check_mark: Best for read-only collections (prevents accidental modification).

:heavy_check_mark: More memory-efficient as it’s immutable.

:heavy_check_mark: Cleaner syntax for creating a list in one line.

:rotating_light: When to avoid?

If you need to modify the list (add/remove elements), this approach won’t work as it throws UnsupportedOperationException.