Download as PDF, PPTX
Uploaded byPremanand Chandrasekaran
Functional Programming in Java
The document discusses functional programming in Java, highlighting its evolution from Java 6 to Java 8. It details tasks related to inventory management, demonstrating the benefits of using functional programming techniques such as lambdas and method references. The author emphasizes the modular, side-effect free nature of functional programming, while also cautioning against excessive use of certain libraries that can lead to verbose and confusing code.
More Related Content
Similar to Functional Programming in Java
Functional Programming in Java
- 1. Functional Programming in Java PremChandrasekaran & Jorge Lee ThoughtWorks Inc. Jan 29th 2014
- 2.
- 3.
- 4.
- 5.
- 6.
- 7. Task 1 -Print names of all items in inventory
- 8.
- 9. Task 2 -Print names of all in-stock items of a category
- 10.
- 11.
- 12. Issues? • Too much duplication • Notsustainable • Too brittle
- 13. Issues? We need toexternalize the search criteria
- 14.
- 15.
- 16.
- 17.
- 18.
- 19.
- 20.
- 21. Task 3 -Search for Products by name
- 22.
- 23.
- 24.
- 25.
- 26.
- 27.
- 28. That’s It! ForJava 6
- 29.
- 30.
- 31. Refactor #3 -Lambdas
- 32. Refactor #4 -No Types Necessary
- 33. Refactor #5 -Method References
- 34. Java 8 Gyaan • FunctionalInterface • Interface with a single method without an implementation • Can be enforced using the @FunctionalInterface annotation • There are several standard functional interfaces defined in the java.lang.function package
- 35.
- 36.
- 37.
- 38. Task 4 -Filter in-stock items and print the Item not just its name
- 39.
- 40.
- 41.
- 42. Task 5 -Print the number of items in inventory
- 43.
- 44. What are wedoing? 1. Providing an initial/default value 2. Accumulating a result 3. Combining the result
- 45.
- 46.
- 47.
- 48.
- 49. Task 6 -Print number of items in all our warehouses
- 50.
- 51.
- 52.
- 53. Task 7 -Print the item with the least amount across warehouses
- 54.
- 55.
- 56.
- 57.
- 58.
- 59. Why Functional? • A newerdifferent way of thinking • More modular • Side-effect free programs • Immutable programs • • Easier to write concurrent code Easier to test
- 60. What to doin Java 6? • Look in the Guava or Apache Commons Lang3 library • But… “As of Java 7, functional programming in Java can only be approximated through awkward and verbose use of anonymous classes. This is expected to change in Java 8, but Guava is currently aimed at users of Java 5 and above.! Excessive use of Guava's functional programming idioms can lead to verbose, confusing, unreadable, and inefficient code. These are by far the most easily (and most commonly) abused parts of Guava, and when you go to preposterous lengths to make your code "a one-liner," the Guava team weeps.” — Guava Documentation
- 61. What to doin Java 6 • First — Stop Whining • Prefer final variables • Minimize the use of void methods • Avoid use of mutable globals (statics) • Avoid returning nulls • Read Effective Java - And apply learnings!
- 62.