Java Stream Filter

In Java, Stream is a feature introduced in Java 8 to provide a functional programming style to process collections of data. It allows you to perform aggregate functions on collections, such as filtering, mapping, sorting, and reducing.

Filter is one of the intermediate operations in the Stream API. It is used to select elements from a Stream based on a specified condition. The filter method takes a predicate, which is a functional interface that takes an element of the stream as input and returns a boolean value. If the returned value is true, the element is included in the new stream, otherwise it is skipped.

Here’s an example of how to use filter to select even numbers from a list of integers:

List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
List<Integer> evenNumbers =
                                    .filter(n -> n % 2 == 0)
System.out.println(evenNumbers); // Output: [2, 4, 6, 8, 10]

In the above code, we created a list of integers and used the stream() method to create a stream of integers. We then applied the filter method to this stream, which selects only the elements that are even. Finally, we collected the filtered elements into a new list using the collect method.

Java Stream filter() example:

Sure, here’s an example of how to use the filter() method in Java:

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

public class StreamFilterExample {
    public static void main(String[] args) {
        List<String> fruits = Arrays.asList("apple", "banana", "orange", "kiwi", "pear");

        // Filter the fruits that start with the letter 'a'
        List<String> filteredFruits =
                .filter(fruit -> fruit.startsWith("a"))

        // Print the filtered fruits
        System.out.println(filteredFruits); // Output: [apple]

In the above example, we created a list of fruits using the Arrays.asList() method. We then created a stream of fruits using the stream() method. We applied the filter() method on this stream, which takes a predicate (in this case, a lambda expression fruit -> fruit.startsWith("a")) that returns true for elements that start with the letter “a”. Finally, we collected the filtered fruits into a new list using the collect() method.

The output of the above code will be [apple], since only the fruit “apple” starts with the letter “a”.