Data Oriented Programming in Java 21, Solving the Countdown game - JEP Cafe #22

In this JEP Café, we will use a lot of the new features added to the JDK in the context of the Data Oriented Programming support: Records, Sealed Types, Pattern Matching, Unnamed Patterns, Exhaustive Switches, as well as the most recent additions to the Stream API: mapMulti(), and Gatherers (a preview feature of the JDK 22). As a bonus, you will see an anonymous class used as a non-denotable type in action, to create a small wrapper on a mutable content. All this is used to solve a funny problem: the Countdown game, where you need to reach a target with a set of randomly drawn numbers, and the four arithmetic operations. Let us check if all this can take us to an efficient, and readable solution. You can watch all the episodes on the JEP Café series here: https://www.youtube.com/playlist?list=PLX8CzqL3ArzV4BpOzLanxd4bZr46x5e87 You can find the code of this episode here: https://gist.github.com/JosePaumard/ee935c53f942a25c3cd38027ce4e31c3 ⎯⎯⎯⎯⎯⎯ Chapters ⎯⎯⎯⎯⎯⎯ 0:00 Do you feel like a coffee break? 0:11 Introducing the Countdown game and its rules 03:01 Introducing the Haskell algorithm translated to Java 04:44 Computing all the permutations of all the subsets 07:20 Splitting the sets to apply the four operations 08:53 Filtering the invalid operations 09:55 Computing the final result and the string of characters 10:21 Using Data Oriented Programming to model the data 12:05 Wrapping up this algorithm 14:49 Writing a bottom up algorithm leveraging Data Oriented Programming 17:32 Using Optional to discard invalid mapping operations 19:30 Getting rid of Optional with Stream.mapMulti() 21:37 Implementing resolve() with an exhaustive switch and pattern matching 23:00 Using a Gatherer to inserting an element at a specific place in a sorted stream 27:18 Using anonymous classes and non-denotable types 28:23 Using the Gatherer in the final process 29:00 Making the algorithm efficient 30:59 Writing the final algorithm using Records 31:50 Comparing the two algorithms 32:33 That's it for today, talk to you soon! ⎯⎯⎯⎯⎯⎯ Resources ⎯⎯⎯⎯⎯⎯ Some amazing Countdown episodes! ◦ 25 50 75 100 3 6 ➱ 952 https://youtu.be/pfa3MHLLSWI ◦ 25 50 75 100 1 10 ➱ 813 https://youtu.be/_JQYYz92-Uk ◦ 100 9 5 10 4 2 ➱ 566 https://youtu.be/Lbhxv5QPErM ◦ 50 75 100 25 2 1 ➱ 940 https://youtu.be/0q6PT4ad6BY ◦ 75 25 50 100 8 2 ➱ 431 https://youtu.be/mRLW_iZVmHU ◦ 25 100 75 50 6 4 ➱ 821 https://youtu.be/sKdM82SELsU ◦ 3 1 7 8 1 4 ➱ 246 https://youtu.be/hJf3BYnz5NQ More resources on Data Oriented Programming and other subjects covered in this JEP Café ◦ Solving the Countdown problem with Java 21's Language Features by Sundar Athijegannathan ➱ https://inside.java/2023/11/03/countdown-haskell-java/ ◦ Prof. Graham Hutton ➱ https://www.cs.nott.ac.uk/~pszgmh/ ◦ Haskell ➱ https://haskell.org/ ◦ Haskell Demo by Prof. Graham Hutton ➱ https://youtu.be/Qmi6T2AKA3k ◦ The JEP 461 about Stream Gatherers ➱ https://openjdk.org/jeps/461 ◦ Nicolai on Gatherers ➱ https://youtu.be/epgJm2dZTSg and https://youtu.be/pNQ5OXMXDbY ◦ Dev.java ➱ https://dev.java ◦ Inside.java ➱ https://inside.java ◦ JDK 22 ➱ https://openjdk.org/projects/jdk/22 ◦ JDK 21 ➱ https://openjdk.org/projects/jdk/21 ◦ JDK 17 ➱ https://openjdk.org/projects/jdk/17 ◦ OpenJDK ➱ https://openjdk.org ◦ Oracle Java ➱ https://www.oracle.com/java/ Tags: #Java #Java21 #OpenJDK #JDK #JDK21 #JEPCafe #insidejava