Java Stream distinct() Method

The distinct() method in Java, part of the java.util.stream.Stream interface, is used to return a stream consisting of the distinct elements of the original stream. This method is useful when you need to remove duplicates from a stream.

Table of Contents

1. Introduction
2. distinct() Method Syntax
3. Understanding distinct()
4. Examples
   • Basic Usage
   • Using distinct() with Other Stream Operations
5. Real-World Use Case
6. Conclusion

Introduction

The distinct() method returns a stream consisting of the distinct elements of the original stream. This method is particularly useful for scenarios where you need to work with unique values or remove duplicates.

distinct() Method Syntax

The syntax for the distinct() method is as follows:

Stream<T> distinct()

Parameters:

• This method does not take any parameters.

Returns:

• A new Stream consisting of the distinct elements of the original stream.

Throws:

• This method does not throw any exceptions.

Understanding distinct()

The distinct() method processes the elements of the stream and eliminates duplicates, ensuring that the resulting stream contains only unique elements. This is useful for scenarios where you need to work with unique values or when duplicates need to be removed for further processing.

Examples

Basic Usage

To demonstrate the basic usage of distinct(), we will create a Stream with duplicate elements and use distinct() to remove the duplicates.

Example

import java.util.stream.Stream;

public class DistinctExample {
    public static void main(String[] args) {
        Stream<String> stream = Stream.of("apple", "banana", "apple", "cherry", "banana");

        // Use distinct() to remove duplicates
        Stream<String> distinctStream = stream.distinct();

        // Print the distinct elements
        distinctStream.forEach(System.out::println);
    }
}

Output:

apple
banana
cherry

Using distinct() with Other Stream Operations

This example shows how to use distinct() in combination with other stream operations, such as filtering and mapping.

Example

import java.util.stream.Stream;

public class DistinctWithOtherOperationsExample {
    public static void main(String[] args) {
        Stream<String> stream = Stream.of("apple", "banana", "apple", "cherry", "banana");

        // Filter elements starting with 'a', remove duplicates, and convert to uppercase
        Stream<String> processedStream = stream.filter(s -> s.startsWith("a"))
                                               .distinct()
                                               .map(String::toUpperCase);

        // Print the processed elements
        processedStream.forEach(System.out::println);
    }
}

Output:

APPLE

Real-World Use Case

Removing Duplicate Names

In real-world applications, the distinct() method can be used to remove duplicate names from a stream of names.

Example

import java.util.stream.Stream;

public class RemoveDuplicateNamesExample {
    public static void main(String[] args) {
        Stream<String> names = Stream.of("Alice", "Bob", "Alice", "Charlie", "Bob");

        // Use distinct() to remove duplicate names
        Stream<String> distinctNames = names.distinct();

        // Print the distinct names
        distinctNames.forEach(name -> System.out.println("Name: " + name));
    }
}

Output:

Name: Alice
Name: Bob
Name: Charlie

Conclusion

The Stream.distinct() method is used to return a stream consisting of the distinct elements of the original stream. This method is particularly useful for scenarios where you need to remove duplicates and work with unique values. By understanding and using this method, you can efficiently manage and process streams of values in your Java applications, ensuring that only distinct elements are considered for further operations.