Java 8 Tutorial:
Lambda Expressions, Streams, and More

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Following is a series of tutorials on the key new features of Java 8. Since each section includes exercises and exercise solutions, this can also be viewed as a self-paced Java 8 training course. The key to learning is not merely reading, but doing the exercises. After you do each set of exercises, compare your solutions to the ones provided.

These tutorials assume that you already know Java 5 or later, prefarable Java 7; they focus on Java 8 topics that would not be understandable to those without at least moderate knowledge of basic syntax, OOP, and data structures in recent Java versions. If you don't already know the Java language, please see the Java programming tutorial series. All the slides (PDF), source code, exercises, and exercise solutions are free for unrestricted use.

Overview of the Java 8 Tutorial Series

Although lambda expressions are not quite real functions, they are close enough for most purposes, and have very succinct syntax that looks like Scala anonymous functions (minus the type declarations). Although it hardly makes Java into Lisp, lambdas support a definite functional programming style that is long overdue in Java.

Streams are wrappers around collections that use lambdas pervasively. They support many operations that use lambdas, including "map", "reduce", "filter", and "forEach". They also support lazy evaluation, so if you map firstName over Employees, filter ones that start with "P", then choose the first, it really only maps and filters until the first match. Streams can also be parallel, so that the operations are automatically done concurrently, without any explicit multithreading code.

Taken together, lambdas and streams result in by far the biggest change to Java programming since at least 2004, when generics and annotations were added to the language.

These tutorials are derived from Marty Hall's world-renowned live training courses. Customized courses on Java 8 or general Java programming are usually taught on-site at customer locations, but JSF 2, PrimeFaces, Spring, Hibernate, RESTful Web Services, Android, Hadoop, Ajax/jQuery, GWT, Java 7,and Java 8 training courses at public venues are periodically scheduled for people with too few developers for an onsite course. For descriptions of the various other courses that are available, please see the Java EE and Ajax training course page. To inquire about a customized training course at your location, please contact Marty at

If you find these free tutorials helpful, we would appreciate it if you would link to us. Send corrections or feedback on any tutorial to

Java 8: Installation, Setup, and Review of Foundational Topics

Java 8 Lambda Expressions Part 1

Java 8 Lambda Expressions Part 2

Java 8 Lambda Expressions Part 3

Java 8 Lambda Expressions Part 4

Java 8 Streams Part 1

Java 8 Streams Part 2

Java 8 Streams Part 3

File IO in Java 8: Applying the Power of Streams

  • Tutorial section in PDF (best for printing and saving).
  • Tutorial section on SlideShare (preferred by some for online viewing).
  • Topics covered:
    • More on try/catch blocks
      • finally, multicatch, try-with-resources
    • Representing file paths
      • Paths.get
    • Reading files by treating them as streams
      • Files.lines
    • Writing files
      • Files.write
    • Making file reading more flexible by using lambdas
      • Split into two pieces: one for Stream<String> and one for file
      • Define functional interfaces and static methods to avoid repeating boilerplate coded
      • Combine predicates with varargs and Predicate.and
    • Exploring folders by using streams
      • Files.list, Files.walk, Files.find
    • File I/O in Java 7
      • Files.readAllLines
  • Source code of examples in this section. Bundled as an Eclipse project, but can be easily imported into NetBeans or IDEA.
  • Exercises to reinforce the concepts in this section.
  • Exercise solutions.

Customized Onsite Training

Looking for short hands-on training courses on Java 8, general Java programming, JSF 2.2, PrimeFaces, Android development, or other Java-related topics taught at your company? The courses are taught by Marty Hall, an experienced instructor, developer, speaker, and well-known Java EE author, and the creator of this tutorial series. For more information, see the JSF and PrimeFaces training course page, the Java training course page or contact Marty to arrange a course at your location. Courses are available in any country, and have been given in N. America, Central America, Europe, Asia, and Australia. Distinctive features of Marty's training:

  • Experienced instructor who can answer tough questions and show best practices.
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    Marty & Java inventor James Gosling at Marty's car.

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  • Competitive prices. Marty's public training courses are typically at least 20% cheaper than the canned courses from the big training vendors. And his courses include a textbook, a bound student notebook, meals and snacks, exercises, and exercise solutions. Onsite courses at your location are even cheaper, since there are no venue rental costs. Plus, your developers don't have to pay travel costs and the content and pace is customizable.

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PowerPoint Files for University Faculty

The PDF files in this tutorial contain the complete text of the original PowerPoint files, so if your goal is learning this technology, just stick with this tutorial. However, as a service to instructors teaching full-semester courses at accredited universities, will release the original PowerPoint files for free. Please see the instructor materials page for details.

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