3.25 Forcing Everyone To Use Static Methods

Juppies 2 by Dr Heinz M. Kabutz

Next we would like to stop someone from constructing the ArrayShuffler class, since they should be calling the static method instead. The first step is to add a constructor and make it private, like this:

  private ArrayShuffler() {}

When we now try to run our application, we find several places where we called shuffle on an object of type ArrayShuffler, rather than on the class. We fix those to instead call the static method.

Note that when we tried running the code again, it now tried to compile the test classes and those also failed. The tests were not compiled together with the main game, since they are a different part of the system.

We again replace the new ArrayShuffer() code with calling the static method on the class with ArrayShuffler.shuffle().

Everything works, so we commit our 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.