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Simplifying Data Processing with Java Stream API
Java Stream API, introduced in Java 8, revolutionized how developers process data collections. This functional-style approach makes code more readable. In this blog, we’ll dive into a real-world example to demonstrate the power and flexibility of the Java Stream API.
Before we get into the example, let’s briefly look at the core concepts of the Stream API:
Streams: Sequences of elements supporting sequential and parallel operations.
Intermediate Operations: Transform streams into another stream (e.g., map, filter).
Terminal Operations: Produce a result or side effect (e.g., collect, forEach).
Real-World Scenario: E-commerce Order Processing
Step 1: Setting Up the Data Models
public class Customer {
private Long id;
private String name;
private String email;
//constructor,getters and setter, tostring
}
public class Order {
private Long id;
private LocalDate date;
private Customer customer;
private List<Product> products;
private BigDecimal total;
//constructor,getters and setter, tostring
}
public class Product {
private Long id;
private String name;
private BigDecimal price;
//constructor,getters and setter, tostring
}
Step 2: Let’s create some sample orders to work with.
public class SampleData {
public static List<Order> getOrders() {
Customer customer1 = new Customer(1L, "Alice Smith", "[email protected]");
Customer customer2 = new Customer(2L, "Bob Johnson", "[email protected]");
Product product1 = new Product(1L, "Laptop", new BigDecimal("1200.00"));
Product product2 = new Product(2L, "Smartphone", new BigDecimal("800.00"));
Product product3 = new Product(3L, "Tablet", new BigDecimal("600.00"));
Order order1 = new Order(1L, LocalDate.now().minusDays(2), customer1, Arrays.asList(product1, product3), new BigDecimal("1800.00"));
Order order2 = new Order(2L, LocalDate.now().minusDays(1), customer2, Arrays.asList(product2), new BigDecimal("800.00"));
Order order3 = new Order(3L, LocalDate.now(), customer1, Arrays.asList(product1, product2, product3), new BigDecimal("2600.00"));
return Arrays.asList(order1, order2, order3);
}
}
Step 3: Let’s perform various operations on this data using the Stream API.
public class StreamExamples {
//this method will return the total revenue of orders
public static BigDecimal totalRevenue(List<Order> orders){
BigDecimal totalRevenue = orders.stream()
.map(Order::getTotal)
.reduce(BigDecimal.ZERO, BigDecimal::add);
return totalRevenue;
}
//this method will return the list of all products that were sold
public static List<Product> getAllProductsSold(List<Order> orders){
List<Product> productsSold = orders.stream()
.flatMap(order -> order.getProducts().stream())
.distinct()
.toList();
return productsSold;
}
}
Conclusion
The examples above showcase just a few ways you can use the Stream API to handle common tasks in an e-commerce application. As you continue to explore, you’ll find even more opportunities to simplify and enhance your Java code with streams.
References
https://www.baeldung.com/java-8-streams
https://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html
https://www.geeksforgeeks.org/stream-in-java/
GitHub : https://github.com/tharindu1998/StreamAPIBlogExample
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