Java Stream filter() Method with Real-World Examples

Ramesh Fadatare

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4 min read

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Mar 3, 2025

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Learn how to use Java’s Stream filter() method to filter collections efficiently. Apply conditional filtering on numbers, strings, and objects with real-world use cases.

🚀 Introduction to Java Stream filter() Method

The Stream API in Java provides the filter() method, which allows you to process collections and extract elements based on conditions.

✅ What Does filter() Do?

• Filters each element in a stream based on a predicate (boolean condition).
• Produces a new Stream containing only elements that match the condition.
• Improves efficiency by avoiding manual iteration.

💡 Common Use Cases:
✔ Filter even numbers from a list
✔ Extract specific strings from a collection
✔ Filter custom objects based on multiple conditions

📌 In this article, you’ll learn:
✅ How to use filter() with different data types.
✅ How to filter numbers, strings, and custom objects efficiently.
✅ Best practices for using filter() effectively.

1️⃣ Filtering Even Numbers from a List

✔ Traditional Way (Before Java 8)

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

public class StreamFilteringExample {
    public static void main(String[] args) {
        List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10); // Source list

        // ✅ Traditional way of filtering even numbers
        List<Integer> evenNumbers = new ArrayList<>();
        for (Integer number : numbers) {
            if (number % 2 == 0) {
                evenNumbers.add(number);
            }
        }

        System.out.println(evenNumbers); // Output: [2, 4, 6, 8, 10]
    }
}

📌 Problems with this approach?
❌ Verbose — Requires explicit iteration and condition checking.
❌ Less efficient — Iterates over every element manually.

✔ Using Java 8 Stream filter()

import java.util.Arrays;

import java.util.List;

public class StreamFilteringExample {
    public static void main(String[] args) {…