Real-World Examples

Now that we’ve covered the key features of Java 8, let’s see how they can be applied in real-world scenarios. These examples demonstrate how to combine multiple Java 8 features like Lambda Expressions, Streams API, and Optional to solve practical problems.

Example 1: Filtering and Processing a List of Employees

Imagine you have a list of employees, and you want to filter out employees who earn more than a certain salary, sort them by name, and print their details.

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

class Employee {
    private String name;
    private double salary;

    public Employee(String name, double salary) {
        this.name = name;
        this.salary = salary;
    }

    public String getName() {
        return name;
    }

    public double getSalary() {
        return salary;
    }

    @Override
    public String toString() {
        return "Employee{name='" + name + "', salary=" + salary + "}";
    }
}

public class EmployeeExample {
    public static void main(String[] args) {
        List<Employee> employees = Arrays.asList(
            new Employee("Alice", 5000),
            new Employee("Bob", 7000),
            new Employee("Charlie", 6000)
        );

        // Filter employees earning more than 5500, sort by name, and print
        employees.stream()
                 .filter(employee -> employee.getSalary() > 5500)
                 .sorted((e1, e2) -> e1.getName().compareTo(e2.getName()))
                 .forEach(System.out::println);
    }
}

Output:

Employee{name='Bob', salary=7000.0}
Employee{name='Charlie', salary=6000.0}

Explanation:

• The filter method selects employees earning more than 5500.
• The sorted method sorts the filtered employees by name.
• The forEach method prints each employee’s details.

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Example 2: Handling Null Values Safely with Optional

Suppose you’re retrieving a user’s email address from a database, but the value might be null. Using Optional, you can handle this safely without risking a NullPointerException.

import java.util.Optional;

public class OptionalExample {
    public static void main(String[] args) {
        // Simulate fetching an email address (could be null)
        String email = getEmailFromDatabase();

        // Use Optional to handle null values
        Optional<String> optionalEmail = Optional.ofNullable(email);

        // Provide a default value if the email is null
        String result = optionalEmail.orElse("No email available");
        System.out.println("Email: " + result);
    }

    private static String getEmailFromDatabase() {
        // Simulate a null value
        return null;
    }
}

Output:

Email: No email available

Explanation:

• The Optional.ofNullable(email) creates an Optional that may or may not contain a value.
• The orElse method provides a default value ("No email available") if the email is null.

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Example 3: Calculating Total Working Hours with Streams

Suppose you have a list of tasks, each with a duration in hours, and you want to calculate the total working hours using the Streams API.

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

public class WorkingHoursExample {
    public static void main(String[] args) {
        List<Integer> taskDurations = Arrays.asList(2, 3, 5, 4);

        // Calculate total working hours using reduce
        int totalHours = taskDurations.stream()
                                      .reduce(0, Integer::sum);

        System.out.println("Total Working Hours: " + totalHours);
    }
}

Output:

Total Working Hours: 14

Explanation:

• The reduce method combines all elements in the list using the Integer::sum function.
• The result is the total sum of all task durations.

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Example 4: Formatting Dates with the New Date and Time API

Suppose you need to format today’s date in a specific format, such as "dd/MM/yyyy". You can use the new Date and Time API for this.

import java.time.LocalDate;
import java.time.format.DateTimeFormatter;

public class DateFormatExample {
    public static void main(String[] args) {
        // Get today's date
        LocalDate today = LocalDate.now();

        // Format the date
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("dd/MM/yyyy");
        String formattedDate = today.format(formatter);

        System.out.println("Formatted Date: " + formattedDate);
    }
}

Output:

Formatted Date: 05/10/2023

Explanation:

• The LocalDate.now() retrieves today’s date.
• The DateTimeFormatter formats the date into the desired pattern ("dd/MM/yyyy").

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Key Takeaways

• Combine Streams and Lambda Expressions to process collections efficiently.
• Use Optional to handle null values safely and avoid NullPointerException.
• Leverage the new Date and Time API for modern and thread-safe date handling.
• These examples demonstrate how Java 8 features can simplify real-world programming tasks.