How to Find the Third Highest Salary in Each Department Using Java 8 Streams
- Sahadev Bite
- Nov 14, 2024
- 3 min read
Java 8's Stream API provides a powerful and concise way to manipulate collections and process data. One common scenario you may encounter is needing to analyze employee data—specifically, finding the 3rd highest salary within each department. In this blog post, we'll walk through how to achieve this using Java 8 streams.
Table of Contents
Introduction
Employee Data Example
Grouping by Department and Finding the 3rd Highest Salary
Handling Departments with Less Than 3 Employees
Simplifying the Code with Additional Collectors
Extracting Just the 3rd Highest Salary Value
Conclusion
Introduction
When working with a list of employees, it's common to need insights like sorting employees by salary and grouping them by their department. With the Java 8 Stream API, these tasks become more straightforward and expressive. In this post, we'll demonstrate how to:
Group employees by their department.
Sort employees in descending order by salary within each department.
Find the employee who ranks 3rd in salary within each department.
We'll provide a complete code example and break down each step of the solution, ensuring even complex tasks remain manageable and easy to understand.
Employee Data Example
Let's start with a simple Employee class and a list of employees from various departments with different salaries:
Here's a sample list of employees:
Grouping by Department and Finding the 3rd Highest Salary
To find the 3rd highest salary in each department, we can:
Group employees by department.
Sort employees within each department by salary in descending order.
Find the employee with the 3rd highest salary.
We can achieve these steps with the Stream API as shown below:
How It Works
Grouping by Department: We use Collectors.groupingBy(Employee::getDepartment, ...) to group employees by their department. This creates a map where each department name is associated with a list of employees from that department.
Sorting by Salary: The collectingAndThen and sorted operations sort employees in descending order by their salary (Comparator.comparingInt(Employee::getSalary).reversed()).
Finding the 3rd Highest: Using .skip(2), we skip the first two employees in each sorted list (those with the highest and second-highest salaries), and .findFirst() returns the 3rd highest salary employee.
Output
Handling Departments with Less Than 3 Employees
If a department has fewer than 3 employees, the Optional<Employee> returned by findFirst() will be empty after skipping two. We can handle these scenarios gracefully:
This additional check ensures we handle departments where the 3rd highest salary doesn't exist.
Simplifying the Code with Additional Collectors
We can simplify our code further by using collectingAndThen to directly store the employee or null if not found:
Explanation
collectors.collectingAndThen(...): We use collectingAndThen to transform the result of the collector Collectors.toList() before storing it in the Map.
Returning Employee or Null: By using .orElse(null), we store either the Employee object found at the 3rd highest salary position or null if none exists.
Output:
Extracting Just the 3rd Highest Salary Value
If you're only interested in the salary value of the 3rd highest earner in each department, you can adapt the stream operations to return just the salary:
Explanation
map(Employee::getSalary): This step maps the Employee objects to their salary values.
Third Highest Salary: The code now directly extracts and stores the 3rd highest salary as an integer.
Conclusion
In this blog post, we've explored how to find the 3rd highest salary in each department using Java 8 Stream API. We covered:
Grouping employees by department.
Sorting employees by salary in descending order within each department.
Extracting the 3rd highest salary or employee details.
Handling cases where a department has fewer than 3 employees.
Simplifying the code using Collectors.collectingAndThen.
The Java 8 Stream API offers a powerful, concise way to handle complex operations on collections. Understanding how to use methods like groupingBy, collectingAndThen, and sorted combined with stream operations like skip and findFirst can help you effectively solve similar data processing tasks in your applications.
We hope this explanation helps you master these concepts and apply them to your projects. If you have any questions or would like to see more examples, please leave a comment below!
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