Java Stream distinct() Tutorial 🎯

Welcome to the Java Stream distinct() tutorial! In this comprehensive guide, we'll explore the distinct() method, which is an essential tool for dealing with duplicate elements in a Stream. Let's dive in! 🐳

What is Java Stream distinct()? 📝

The distinct() method is used to eliminate duplicate elements from a Stream. It returns a new Stream that contains only unique elements based on the equals() method.

Prerequisites 💡

Before we get started, it's important to have a basic understanding of the following topics:

Using distinct() 🎯

To use the distinct() method, you simply call it on the Stream and pass no arguments. Let's see an example:

java

import java.util.Arrays;
import java.util.stream.Stream;

public class Main {
    public static void main(String[] args) {
        int[] numbers = {1, 2, 2, 3, 4, 4, 5};
        Stream<Integer> stream = Arrays.stream(numbers);
        Stream<Integer> distinctNumbers = stream.distinct();

        distinctNumbers.forEach(System.out::println);
    }
}

Output:

In the example above, we have an array of integers with duplicate values. By creating a Stream from the array and using the distinct() method, we obtain a new Stream containing only unique elements.

💡 Pro Tip:

The distinct() method processes the Stream only once, so it's an efficient way to remove duplicates.

Using distinct() with Custom Comparator 🎯

In some cases, you might need to compare elements based on a custom logic. In those situations, you can provide a custom Comparator to the distinct() method:

java

import java.util.Arrays;
import java.util.Comparator;
import java.util.stream.Stream;

public class Main {
    public static void main(String[] args) {
        String[] names = {"Alice", "Bob", "Alice", "Charlie", "Eve", "Eve"};
        Stream<String> stream = Arrays.stream(names);
        Comparator<String> caseInsensitiveComparator = Comparator.comparing(String::toLowerCase);
        Stream<String> distinctNames = stream.sorted(caseInsensitiveComparator).distinct();

        distinctNames.forEach(System.out::println);
    }
}

Output:

Alice
Bob
Charlie
Eve

In the example above, we have an array of strings with duplicate names (case sensitive). By using a custom Comparator that converts all strings to lowercase, we can sort and remove duplicates effectively.

Quiz 💡

And that's it for our Java Stream distinct() tutorial! With this knowledge, you can now effectively deal with duplicate elements in your Java projects. Happy coding! 🎉