java

Functional Java: Lambda & Streams

Replace loops with Lambdas and Streams for readable, crash-safe, and efficient data processing in modern Java.

Expected Outcome

Ability to write declarative code, build elegant data streams, and handle edge cases in a type-safe manner.

Target Audience

For developers wanting to write cleaner and more readable code using modern declarative patterns.

Prerequisites

Java experience is required, for beginners 'Java Jumpstart: Essentials' is recommended first.

Curriculum & Highlights

→ Lambdas & Method References

→ Functional Interfaces

→ Streams API (Filter, Map)

→ Data Grouping (Collectors)

→ Debugging with Peek

→ Type Safety with Optional

→ Parallel Streams (N*Q Rule)

Challenges we address

"How do you shift from imperative code to a declarative mindset using Lambdas?"

"How do we dynamically group and aggregate large datasets with Streams and Collectors?"

"When is a Parallel Stream actually faster, and how do you use Optional correctly?"

Detailed Description

Traditional Java code is often filled with anonymous inner classes, extensive for-loops, and complex if-else structures that obscure actual business logic. Without a declarative mindset, data transformations become unnecessarily heavy to maintain, and unhandled searches often result in unwanted NullPointerExceptions as systems scale in production. This workshop introduces a modern way of programming through our Active Learning methodology. We cover how to eliminate boilerplate with Lambdas and Method References, and then build elegant data streams using The Streams API. The result is concise, readable pipelines that focus on what the code should achieve, eliminate null risks via Optional, and prepare the application for performance optimization through multi-threaded execution. We start by demystifying the underlying functional interfaces (such as Predicate and Consumer) to truly understand how Java maps behaviors to types. With this foundation, we build immutable data pipelines where filter and map replace mutable state. For more complex structures, we dive deep into the Collectors utility to dynamically group, join, and partition data. We also discuss the architecture of functional code and how to efficiently debug encapsulated chains using the peek method. In the final section, we focus on stability and extreme scale. We learn to eliminate defensive null checks by designing safe APIs with Optional, analyzing common anti-patterns tied to its usage. Finally, we explore Parallel Streams to process millions of rows of data across multiple CPU cores. Through a practical architecture discussion around the critical 'N * Q' rule, we learn to evaluate exactly when parallel execution provides decisive performance gains, and when it merely creates unwanted overhead.

Recommendation & Next Steps

Secure the logic of your functional streams by moving on to 'TDD & JUnit: Quality in Java' to build a complete testing strategy. →

Format Workshop

Duration 1 day

Level Professional

Instructor Andreas Olsson

Price per group $2,900

Standard price per group (up to 12 participants) for remote delivery. Additional costs apply for onsite delivery.

Get Quote & Book Download Overview (PDF)

Tech Stack

Functional Streams Lambdas Clean Code Java 21 Java 25

Your Instructor

Andreas Olsson

Expertise through Active Learning

Java and the Spring Framework have been my core focus for over 20 years. Today, my mission is primarily to help organizations step into the future by integrating intelligent agents and AI-driven features into modern Java systems.

Actlea stands for Active Learning – the philosophy that programming is best learned by writing code, not by watching slides. My workshops focus on intensive, hands-on exercises designed to solve real-world problems.

I deliver proven training concepts globally across all timezones. While I specialize in remote delivery, I love to travel for onsite workshops. My modules are ready for immediate impact but can be tailored to your team's specific requirements.

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Java • Spring Boot • Spring AI

Enterprise teams trained by Actlea

Participant Reviews

What past participants say

Read about the pedagogical approach, the hands-on labs, and the impact on daily work.

"The Java program at Academic Work was excellent! It consisted of, given the name, mostly programming in Java, but also had some front-end courses. I thought the Java courses were the best. Not only because I was most interested in java, but also because the teacher in the java courses was Andreas. It's easy for it to get messy and "too much" when learning programming, especially for those starting from scratch, but Andreas taught in a very pedagogical way, and it never became long-winded or boring. Recommends the java program at Academic Work to anyone who wants to learn programming and wants to change careers."

"Andreas is a very positive and easy-going individual, but above all a fantastic educator. His teaching method and structure is adapted for everyone from beginners to experienced participants. Quick to provide personal assistance, called up on video chat and took his time. I appreciated all the Java days, I am so satisfied and grateful with the foundation I got with me. Strongly recommend. Rating 5 out of 5 stars! ⭐️⭐️⭐️⭐️⭐️"

"I had the honor of having Andreas as a teacher during a 12 week Java program for Brights. During these weeks we learned the basics of Java but also more advanced Java. Would really recommend Andreas for the great competence he possesses but also for his patience. He always answered the questions that we students had and was very patient when required. Andreas always has a smile on his face and he is passionate about teaching, which you can clearly see. I always felt safe talking to Andreas when I needed help and he was always there to support. He is simply one of the best teachers I have ever had!"

"I recently had the pleasure of being a student of Andreas and I cannot speak highly enough of his skill and professionalism. Throughout the training, Andreas demonstrated a deep understanding of Java programming and was able to convey complex concepts in a way that was easy to understand. His ability to break down difficult topics and explain them in a clear and concise manner was truly remarkable. Overall, I would highly recommend Andreas as a teacher of Java programming. His skill and professionalism make him an exceptional educator, and I am grateful to have had the opportunity to learn from him. If you are looking for a teacher who is knowledgeable, patient and passionate about teaching, Andreas is the perfect choice."

"I attended a 12-week training in Java where I had Andreas as a teacher most of the time. He has a very good and pedagogical way of teaching that made it easy to understand, even for someone like me who had no prior knowledge of Java, I had no problems following the presentations. In addition to a good teaching method, Andreas is a nice person and easy to communicate with, which made it very easy for us students to ask for help or give feedback during the course. This made the class always have a pleasant atmosphere and I always looked forward to the next day throughout the course."

"Andreas is a fantastic teacher! In addition to the fact that I experienced him as competent with a solid knowledge of his subjects, he really excels as an educator. Regardless of who you are or what level of knowledge you are at, Andreas always responds to one's questions with commitment, curiosity and a positive attitude that is contagious. Above all, I appreciated that he both gave me space to explore solutions myself and think creatively, while he was always there to contribute his support. I highly recommend Andreas!"

"My name is Rabia and I participated in the Java Developer course with Andreas starting January 2022 after 20 years in the banking and finance industry. Previously had no experience whatsoever in the IT world, but chose the track with the digitization the world is going through. The course was incredibly broad & intensive and gave a good overview. When the course was over, I was hired by Capgemini as a junior developer. During the course I probably complained many times about how much information it presented, but I have benefited greatly from everything I have been taught. I continue to learn every day but have an understanding that still amazes me when I realize how much I brought with me. Thanks Andreas for everything! The course has given me the opportunity to pursue a new career in a new industry that I love. The change has given me new energy and opened up new doors. I am so grateful!"

"What makes Andreas such a good teacher is that his understanding of the subject is so clearly visible. If you ask a question that only scratches the surface of a problem, you can be sure that you will get an answer where Andreas makes sure that you not only understand the short answer, but also a developing answer where he explains why it works this way and what the underlying structure of this is. Andreas has a way of breaking down even more complex problems into more manageable pieces for us students."

"Throughout the training, Andreas was endlessly positive in his dealings with all the consultants he trained. There is an enormous amount of information that you need to consume during an Accelerated Learning program, which can easily lead to frustration. Having a competent and experienced teacher in Andreas, who can both teach the modules in an efficient and fun way, as well as constantly be positive and encouraging throughout the process, undeniably eased the weight on everyone's shoulders."

"Andreas is a fun and dedicated teacher who always took time for questions. When you needed help, you always got it, no matter how long it took. Andreas has a cheerful mood that is contagious, which means that there was always a pleasant atmosphere during his lectures. He is very educational in his way of being, which makes it easy to absorb the information."

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