3.19 Expression Lambdas

Juppies 2 by Dr Heinz M. Kabutz

Lambdas with a single statement do not need the curly braces and can be written as an "expression lambda". Note that our IDE has a thin line that indicates how wide the line should be. When I was a little boy, my father was studying at university and one of the classes he took was Fortran programming. We had all these printouts and punched-cards that we used to play with, pretending they were some secret access cards. Punched-cards were typically 80 characters wide, and this number has stuck through decades of coding. Even though I am using a 4k Dell monitor, the default line length is still set to 80 characters. This does seem to be a reasonable human limit. Make it much longer, and it becomes difficult to read. You might want to increase it 120 if your team agrees.

We replace the SORTED_SCRAMBLER statement lambda with an expression lambda.

In order to also change the RANDOM_SCRAMBLER to an expression lambda, we need to first inline the new ArrayShuffler() to where the shuffler variable is currently used. We can do that manually by selecting the new ArrayShuffler(), cutting it, and pasting it on top of the shuffler in the line underneath. We then delete the ArrayShuffler variable declaration.

When we change the layout of our code, we need to remember that this is very much a matter of preference. It is a good idea to be able to comfortably read a lot of different coding styles. When we work in someone else's code base, it is polite to use whatever coding style they used for their code.

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Table of Contents

• 0.1: Programming is a team sport - source control
• 0.2: Creating an account on GitHub
• 0.3: Forking the Juppies2 repository from kabutz
• 0.4: Oracle JDK
• 0.5: Oracle OpenJDK
• 0.6: Azul's Zulu OpenJDK
• 0.7: Installing the Oracle OpenJDK
• 0.8: Integrated Development Environments (IDEs)
• 0.9: Downloading Apache NetBeans
• 0.10: Loading our Juppies2 Project in Apache NetBeans
• 0.11: Running the AnagramGame with Apache NetBeans
• 0.12: Downloading IntelliJ IDEA Community Edition
• 0.13: Installing IntelliJ IDEA Community Edition
• 0.14: Running the AnagramGame with IntelliJ IDEA Community Edition
• 0.15: Downloading and Installing Eclipse
• 0.16: Running the AnagramGame with Eclipse
• 1.1: AnagramGame Project Structure
• 1.2: WordLibrary
• 1.3: Swing User Interface (UI)
• 1.4: Buffer Overflows
• 1.5: Demo of New Word Button
• 1.6: Demo of Guess Button
• 1.7: StaticWordLibrary Structure
• 1.8: StaticWordLibrary Details
• 1.9: Changing the Size of Our StaticWordLibrary
• 1.10: How my Buffer Overflow Wiped my Colleague's Hard Disk
• 1.11: Adding Our Own Words to the StaticWordLibrary
• 1.12: WordLibraryTest With JUnit
• 1.13: Java's For Loop
• 1.14: Testing That Words Are Anagrams
• 1.15: Running JUnit
• 1.16: isAnagram() Method
• 1.17: Fixing StaticWordLibrary
• 1.18: WordLibraries Facade
• 1.19: Find Usages
• 1.20: Exercise
• 1.21: Commiting Changes
• 1.22: GitHub Repository
• 1.23: Pushing Commits to Remote Repository on GitHub
• 1.24: Until Next Time
• 2.1: Welcome back
• 2.2: Setting up NetBeans Git Toolbar
• 2.3: Creating a Git Branch for Today's Session
• 2.4: Typical Directory Structure Under Maven
• 2.5: NetBeans Magic Shortcuts
• 2.6: Avoid Copy & Paste Programming
• 2.7: Creating a ShuffledWordLibrary
• 2.8: Integer Array for Shuffled Indexes
• 2.9: Finishing the methods to delegate to the other WordLibrary
• 2.10: Trying out the "ShuffledWordLibrary" That Does Not Really Shuffle
• 2.11: Committing Our Changes to Git
• 2.12: Shuffling the Integer Array
• 2.13: Trying Out the Shuffled Anagram List
• 2.14: Committing our "shuffle" method
• 2.15: ArrayShuffler
• 2.16: Creating an ArrayShufflerTest
• 2.17: Printing the indexes array
• 2.18: Fixing Random to be more random
• 2.19: Extending the Tests
• 2.20: The Goat, The Wolf and The Cabbage (Swapping Integer Values)
• 2.21: Testing the Integer Swapping Code
• 2.22: Testing Before Running Application
• 2.23: Fixing the Integer Swapping Code
• 2.24: Integer Swapping With XOR
• 2.25: Value of Source Control Systems
• 2.26: Changed WordLibrary from an Abstract Class to an Interface
• 2.27: Commit and Push
• 2.28: Until Next Time
• 3.1: Welcome back
• 3.2: Create a new Git Branch
• 3.3: ScrambledWordLibrary
• 3.4: SortedScrambledWordLibrary
• 3.5: Committing Entire Project At Once
• 3.6: Creating a RandomScrambledWordLibrary
• 3.7: Adding a shuffle(char[]) method
• 3.8: Testing the shuffle() method
• 3.9: Scrambler Strategy Extracted
• 3.10: Rot13Scrambler
• 3.11: OriginalScrambler
• 3.12: Moving Scrambler Interface Into ScrambledWordLibary Using IntelliJ IDEA
• 3.13: Moving Shuffler Implementations Into ScrambledWordLibrary
• 3.14: Danger of Overusing Inner Classer
• 3.15: Testing Refactoring
• 3.16: Beauty of IDE Interoperability
• 3.17: Anonymous Inner Classes
• 3.18: Converting Anonymous Inner Class to Lambda
• 3.19: Expression Lambdas
• 3.20: Font Ligatures
• 3.21: Testing and Commiting Lambdas
• 3.22: Turning Rot13Scrambler into a Lambda
• 3.23: Method References
• 3.24: Making ArrayShuffler.shuffle() Methods static
• 3.25: Forcing Everyone To Use Static Methods
• 3.26: DecoratedWordLibrary
• 3.27: ScrambledWordLibrary as a Decorator
• 3.28: ShuffledWordLibrary as a Decorator
• 3.29: Cleaning Up the Concrete Decorators
• 3.30: Updated Copyright Notices
• 3.31: Make Classes Final Where Possible
• 3.32: Commit and Push
• 3.33: Conclusion

We hope you enjoyed this tutorial. If you did, you will also enjoy our courses. We suggest you start with Extreme Java - Advanced Java, followed by Extreme Java - Concurrency Performance for Java 8.