Java lambda filter example
In Java, the introduction of the Lambda expression has made it easier to write concise and readable code. One of the key functionalities that Lambdas provide is the ability to filter data from a collection. This article will explain the process of filtering data using a Lambda expression in Java.
What is a Lambda Expression?
A Lambda expression is a short and anonymous function that can be passed around as a data type. It can be assigned to a variable or passed as an argument to a method. In Java, Lambda expressions are used to write functional interface implementation in a more concise manner.
What is the Filter Function?
The filter function is used to extract elements from a collection that match a certain condition. This can be achieved in Java using the filter method available in the Stream API. The filter method takes a Predicate<T> as an argument, where T is the type of the data being filtered. A Predicate is a functional interface that takes an object and returns a boolean value.
Example:
Consider a collection of Integer objects. We want to extract all the even numbers from the collection. The following example demonstrates how to do this using the filter method in Java.
Filename: LambdaFilterExample.java
import java.util.Arrays;
import java.util.List;
import java.util.function.Predicate;
public class LambdaFilterExample {
public static void main(String[] args) {
List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
Predicate<Integer> evenNumber = num -> num % 2 == 0;
numbers.stream()
.filter(evenNumber)
.forEach(System.out::println);
}
}
Output:
24
6
8
10
In the example, the list of numbers is created using the Arrays.asList method. The filter method is called on the stream of numbers and the evenNumber Predicate is passed as an argument. The filter method returns a stream of all the elements that match the condition specified in the Predicate. Finally, the forEach method is called on the filtered stream, which prints all the even numbers to the console.
The filter method is a very useful tool for data processing and can be used in a variety of scenarios. For example, you can use it to filter data from a database, extract specific values from a collection, or process data in real-time. In this article, we have demonstrated how to use the filter method with a Lambda expression to extract even numbers from a list. However, the same technique can be applied to filter data from any collection type and the Predicate can be used to specify any condition.
Another advantage of using the filter method is that it is very efficient in terms of performance. It is a lazy operation, which means that it does not process the entire stream of data at once, but instead processes the data one element at a time as needed. This can be very useful when working with large amounts of data as it can help to reduce memory usage and processing time. In addition, the filter method is highly composable, which means that you can chain multiple filter operations together to create more complex filtering conditions. For example, you can use multiple filter methods to extract data based on multiple conditions. You can also combine the filter method with other functional operations such as map, reduce, or collect to perform more complex data processing tasks.
In summary, the filter method in Java is a versatile and efficient tool for data processing. When combined with Lambda expressions, it makes it easy to write concise and readable code for filtering data. Whether you're working with a small amount of data or processing large amounts of data in real-time, the filter method is a valuable tool to have in your Java development toolkit. the filter method in Java is a versatile and efficient tool for data processing. When combined with Lambda expressions, it makes it easy to write concise and readable code for filtering data. Whether you're working with a small amount of data or processing large amounts of data in real-time, the filter method is a valuable tool to have in your Java development toolkit. the filter method in Java is a powerful tool for extracting data from collections based on certain conditions. The use of Lambda expressions makes it easier to write readable and concise code for filtering data.