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Java8
This document provides an outline and overview of new features in Java 8. It discusses behavior parameterization through lambda expressions and method references, which allow passing behaviors as arguments in place of anonymous classes. It also covers the Stream API for functional-style processing of collections, Optional as an alternative to null, default methods to allow interfaces to evolve, and CompletableFuture for composable asynchronous programming. Finally, it notes some potential downsides of Java 8 like longer debugging with lambdas and limitations of its functional support.
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Java8
- 1. INTRO TO JAVA8 SHIJIE ZHANG
- 2. OUTLINE ▸What will Java8 give us ▸Behavior parameterization ▸More comprehensive functional interface ▸Lambda expression ▸Method reference ▸Simple syntactic sugar - new methods inside Collections ▸Functional programming - Stream API ▸Intuition ▸Intermediate and terminal operations ▸Properties ▸Alternative to NULL — Optional ▸Changeable Interface — Default methods ▸Asynchronous programming enhancement - Future vs CompletableFuture ▸Other features ▸Dark side of Java 8 ▸Conclusion
- 3. WHAT WILL JAVA8 BRING US CLIMATE IS CHANGING ▸ Java was in dominant positions due to its simplicity, portability, safety and free to use. ▸ JVM-based dynamic language comes up, known for their simplicity and portability. (Groovy, Clojure, Scala) ▸ Big data is on the rise. Programmers need to deal with large collections. ▸ Multicore processor is becoming more and more popular. Programmers need to an easier way to do parallel programming. ▸ Java is kind of verbose.
- 4. WHAT WILL JAVA8 BRING US
- 5. OUTLINE ▸What will Java8 give us ▸Behavior parameterization ▸More comprehensive functional interface ▸Lambda expression ▸Method reference ▸Simple syntactic sugar - new methods inside Collections ▸Functional programming - Stream API ▸Intuition ▸Intermediate and terminal operations ▸Properties ▸Alternative to NULL — Optional ▸Changeable Interface — Default methods ▸Asynchronous programming enhancement - Future vs CompletableFuture ▸Other features ▸Dark side of Java 8 ▸Conclusion
- 6. OUTLINE ▸What will Java8 give us ▸Behavior parameterization ▸More comprehensive functional interface ▸Lambda expression ▸Method reference ▸Simple syntactic sugar - new methods inside Collections ▸Functional programming - Stream API ▸Intuition ▸Intermediate and terminal operations ▸Properties ▸Alternative to NULL — Optional ▸Changeable Interface — Default methods ▸Asynchronous programming enhancement - Future vs CompletableFuture ▸Other features ▸Dark side of Java 8 ▸Conclusion
- 7. BEHAVIOR PARAMETERIZATION -LAMBDAS More comprehensive functional interface ▸ Comparator is an interface. More exactly, a functional interface.
- 8. BEHAVIOR PARAMETERIZATION -LAMBDAS More comprehensive functional interface ▸ Functional interface: an interface has exactly one abstract method ▸ Several functional interface exists before Java 8 ▸ Functional interface enables behavior parameterization
- 9. BEHAVIOR PARAMETERIZATION -LAMBDAS
- 10. BEHAVIOR PARAMETERIZATION -LAMBDAS Where to use functional interface ▸ Anywhere an object could be used ▸ method arguments/parameters/return types ▸ inside collections ▸ Variables ▸ …….
- 11. BEHAVIOR PARAMETERIZATION -LAMBDAS In the past, use anonymous class as instance for functional interface Now, use lambda expression/method reference as instance for functional interface ▸ Think about Comparator — create an anonymous class ▸ All anonymous class could be replaced with lambda/method reference ▸ Anonymous class ~ lambda expression ~ method reference ▸ lambda expressions ▸ method reference
- 12. OUTLINE ▸What will Java8 give us ▸Behavior parameterization ▸More comprehensive functional interface ▸Lambda expression ▸Method reference ▸Simple syntactic sugar - new methods inside Collections ▸Functional programming - Stream API ▸Intuition ▸Intermediate and terminal operations ▸Properties ▸Alternative to NULL — Optional ▸Changeable Interface — Default methods ▸Asynchronous programming enhancement - Future vs CompletableFuture ▸Other features ▸Dark side of Java 8 ▸Conclusion
- 13. BEHAVIOR PARAMETERIZATION -LAMBDAS Lambdas definition ▸ Definition ▸ Examples: 1. ( ) -> { } 2. ( ) -> “Raoul” 3. ( ) -> { return “Mario”;} 4. ( Integer i ) -> return “Alan” + i; 5. ( String s ) -> { “Iron Man”; }
- 14. BEHAVIOR PARAMETERIZATION -LAMBDAS Lambdas definition ▸ Definition ▸ Examples: 1. ( ) -> { } 2. ( ) -> “Raoul” 3. ( ) -> { return “Mario”;} 4. ( Integer i ) -> return “Alan” + i; 5. ( String s ) -> { “Iron Man”; }
- 15. BEHAVIOR PARAMETERIZATION -LAMBDAS Lambda use cases - whenever you use anonymous class
- 16. BEHAVIOR PARAMETERIZATION -LAMBDAS
- 17. BEHAVIOR PARAMETERIZATION -LAMBDAS Type reference Restriction on local variables ▸ Definition
- 18. OUTLINE ▸What will Java8 give us ▸Behavior parameterization ▸More comprehensive functional interface ▸Lambda expression ▸Method reference ▸Simple syntactic sugar - new methods inside Collections ▸Functional programming - Stream API ▸Intuition ▸Intermediate and terminal operations ▸Properties ▸Alternative to NULL — Optional ▸Changeable Interface — Default methods ▸Asynchronous programming enhancement - Future vs CompletableFuture ▸Other features ▸Dark side of Java 8 ▸Conclusion
- 19. BEHAVIOR PARAMETERIZATION -LAMBDAS Method reference definition ▸ Definition: syntactic sugar for lambda expressions
- 20. BEHAVIOR PARAMETERIZATION -LAMBDAS Rules for converting lambda to method reference ▸ A method reference to a static method ▸ A method reference to an instance method of an arbitrary type ▸ A method reference to an instance method of an existing object
- 21. OUTLINE ▸What will Java8 give us ▸Behavior parameterization ▸More comprehensive functional interface ▸Lambda expression ▸Method reference ▸Simple syntactic sugar - new methods inside Collections ▸Functional programming - Stream API ▸Intuition ▸Intermediate and terminal operations ▸Properties ▸Alternative to NULL — Optional ▸Changeable Interface — Default methods ▸Asynchronous programming enhancement - Future vs CompletableFuture ▸Other features ▸Dark side of Java 8 ▸Conclusion
- 22. SIMPLE SYNTACTIC SUGAR- NEW METHODS INSIDE COLLECTIONS Map interface: getOrDefault method ▸ Definition: getOrDefault(K key, V defaultValue) ▸ Scenario: get a value (may not exist) from a map, do some calculation and put it back
- 23. SIMPLE SYNTACTIC SUGAR- NEW METHODS INSIDE COLLECTIONS Map interface: computeIfAbsent method ▸ Definition: computeIfAbsent(K key, Function mapping) ▸ Scenario: if the key does not exist, compute a value for it.
- 24. SIMPLE SYNTACTIC SUGAR- NEW METHODS INSIDE COLLECTIONS Map interface: forEach method ▸ Definition: forEach(Consumer con) ▸ Scenario: loop through a map
- 25. SIMPLE SYNTACTIC SUGAR- NEW METHODS INSIDE COLLECTIONS Collections interface: removeIf method ▸ Definition: removeIf(Predicate filter) ▸ Scenario: remove an element from the list if specific condition is met
- 26. SIMPLE SYNTACTIC SUGAR- NEW METHODS INSIDE COLLECTIONS Other method ▸ List.sort(Comparator) ▸ Map.putIfAbsent() ▸ Map.replace() / replaceAll() ▸ Map.merge() ▸ Map.compute() / computeIfAbsent() / computeIfPresent()
- 27. OUTLINE ▸What will Java8 give us ▸Behavior parameterization ▸More comprehensive functional interface ▸Lambda expression ▸Method reference ▸Simple syntactic sugar - new methods inside Collections ▸Functional programming - Stream API ▸Intuition ▸Intermediate and terminal operations ▸Properties ▸Alternative to NULL — Optional ▸Changeable Interface — Default methods ▸Asynchronous programming enhancement - Future vs CompletableFuture ▸Other features ▸Dark side of Java 8 ▸Conclusion
- 28. OUTLINE ▸What will Java8 give us ▸Behavior parameterization ▸More comprehensive functional interface ▸Lambda expression ▸Method reference ▸Simple syntactic sugar - new methods inside Collections ▸Functional programming - Stream API ▸Intuition ▸Intermediate and terminal operations ▸Properties ▸Alternative to NULL — Optional ▸Changeable Interface — Default methods ▸Asynchronous programming enhancement - Future vs CompletableFuture ▸Other features ▸Dark side of Java 8 ▸Conclusion
- 29. FUNCTIONAL PROGRAMMING -STREAM API Stream API ▸ What’s wrong with collections? ▸ Much business logic entails database-like operations such as grouping a list by category / find the most expensive dish. (Usually implemented with iterators, could we do it declaratively?) ▸ Big data requires us to utilize multicore processor more frequently. (Usually implemented with fork/join framework introduced in Java 7. Could we save some effort? )
- 30. FUNCTIONAL PROGRAMMING -STREAM API Stream API ▸ Def: fancy iterators over collections ▸ Scenario:
- 31. FUNCTIONAL PROGRAMMING -STREAM API
- 32. FUNCTIONAL PROGRAMMING -STREAM API
- 33. FUNCTIONAL PROGRAMMING -STREAM API How to parallel?
- 34. FUNCTIONAL PROGRAMMING -STREAM API
- 35. FUNCTIONAL PROGRAMMING -STREAM API Parallelization realized by Java 7’s fork/join framework underneath
- 36. FUNCTIONAL PROGRAMMING -STREAM API Stream Definition ▸ Stream definition: fancy “internal” iterators over collections
- 37. FUNCTIONAL PROGRAMMING -STREAM API Notice: iterable only once
- 38. OUTLINE ▸What will Java8 give us ▸Behavior parameterization ▸More comprehensive functional interface ▸Lambda expression ▸Method reference ▸Simple syntactic sugar - new methods inside Collections ▸Functional programming - Stream API ▸Intuition ▸Creating, intermediate and terminal operations ▸Properties ▸Alternative to NULL — Optional ▸Changeable Interface — Default methods ▸Asynchronous programming enhancement - Future vs CompletableFuture ▸Other features ▸Dark side of Java 8 ▸Conclusion
- 39. FUNCTIONAL PROGRAMMING -STREAM API How to create stream? ▸ From arrays ▸ From collections ▸ Custom generators — Stream.generate() / iterate() method ▸ From other popular APIs
- 40. FUNCTIONAL PROGRAMMING -STREAM API Stream operations ▸ intermediate operations ▸ terminal operations
- 41. OUTLINE ▸What will Java8 give us ▸Behavior parameterization ▸More comprehensive functional interface ▸Lambda expression ▸Method reference ▸Simple syntactic sugar - new methods inside Collections ▸Functional programming - Stream API ▸Intuition ▸Creating, intermediate and terminal operations ▸Use cases ▸Alternative to NULL — Optional ▸Changeable Interface — Default methods ▸Asynchronous programming enhancement - Future vs CompletableFuture ▸Other features ▸Dark side of Java 8 ▸Conclusion
- 42. FUNCTIONAL PROGRAMMING -STREAM API Use cases: whenever you want to perform database-like operations ▸ Group/Multi-level group ▸ Filter ▸ Sum/Max/Min/Average/Distinct/Count ▸ Extracting specific properties ▸ ……
- 43. OUTLINE ▸What will Java8 give us ▸Behavior parameterization ▸More comprehensive functional interface ▸Lambda expression ▸Method reference ▸Simple syntactic sugar - new methods inside Collections ▸Functional programming - Stream API ▸Intuition ▸Intermediate and terminal operations ▸Use cases ▸Alternative to NULL — Optional ▸Changeable Interface — Default methods ▸Asynchronous programming enhancement - Future vs CompletableFuture ▸Other features ▸Dark side of Java 8 ▸Conclusion
- 44. ALTERNATIVE TO NULL— OPTIONAL Optional definition: ▸ Def: a container may or may not cannot value - just like reference ▸ Benefit 1: ▸ NullPointerException will always be thrown out during runtime ▸ Optional enforces “empty checking” in grammar during compile time ▸ Benefit 2: ▸ Optional interface supports a set of methods makes handling “empty case” easy
- 45. ALTERNATIVE TO NULL— OPTIONAL Optional use case : ▸ http://www.nurkiewicz.com/2013/08/optional-in-java-8-cheat-sheet.html More use cases:
- 46. OUTLINE ▸What will Java8 give us ▸Behavior parameterization ▸More comprehensive functional interface ▸Lambda expression ▸Method reference ▸Simple syntactic sugar - new methods inside Collections ▸Functional programming - Stream API ▸Intuition ▸Intermediate and terminal operations ▸Properties ▸Alternative to NULL — Optional ▸Changeable Interface — Default methods ▸Asynchronous programming enhancement - Future vs CompletableFuture ▸Other features ▸Dark side of Java 8 ▸Conclusion
- 47. EVOLVING API —DEFAULT METHODS Default method
- 48. EVOLVING API —DEFAULT METHODS Default method ▸ Definition: A way to evolve Interface APIs in a compatible way. ▸ As a result, interface could now have methods with implementation ▸ This means “Java supports multiple inheritance” ▸ How does Java solves traditional “Diamond Problem”? ▸ Three resolution rules ▸ http://www.javabrahman.com/java-8/java-8-multiple-inheritance-conflict- resolution-rules-and-diamond-problem/
- 49. OUTLINE ▸What will Java8 give us ▸Behavior parameterization ▸More comprehensive functional interface ▸Lambda expression ▸Method reference ▸Simple syntactic sugar - new methods inside Collections ▸Functional programming - Stream API ▸Intuition ▸Intermediate and terminal operations ▸Properties ▸Alternative to NULL — Optional ▸Changeable Interface — Default methods ▸Asynchronous programming enhancement - Future vs CompletableFuture ▸Other features ▸Dark side of Java 8 ▸Conclusion
- 50. COMPOSABLE ASYNCHRONOUS PROGRAMMING— COMPLETABLEFUTURE Review: Future ▸ Future is used for asynchronous programming How to combine multiple Future task???
- 51. COMPOSABLE ASYNCHRONOUS PROGRAMMING— COMPLETABLEFUTURE CompletableFuture comes into play
- 52. OTHER NEW FEATURES Othernew features ▸ Date and Time API — Handle time zone, separate concerns ▸ JVM Javascript engine — Nashorn
- 53. OUTLINE ▸What will Java8 give us ▸Behavior parameterization ▸More comprehensive functional interface ▸Lambda expression ▸Method reference ▸Simple syntactic sugar - new methods inside Collections ▸Functional programming - Stream API ▸Intuition ▸Intermediate and terminal operations ▸Properties ▸Alternative to NULL — Optional ▸Changeable Interface — Default methods ▸Asynchronous programming enhancement - Future vs CompletableFuture ▸Other features ▸Dark side of Java 8 ▸Conclusion
- 54. DARKSIDE OF JAVA8 Dark side of Java 8 ▸ Lambda expressions will make debugging log much longer ▸ Not truly functional ▸ Additional reading ▸ http://blog.takipi.com/6-reasons-not-to-switch-to-java-8-just-yet/ ▸ Google search “DZone what’s wrong with Java 8”
- 55. OUTLINE ▸What will Java8 give us ▸Behavior parameterization ▸More comprehensive functional interface ▸Lambda expression ▸Method reference ▸Simple syntactic sugar - new methods inside Collections ▸Functional programming - Stream API ▸Intuition ▸Intermediate and terminal operations ▸Properties ▸Alternative to NULL — Optional ▸Changeable Interface — Default methods ▸Asynchronous programming enhancement - Future vs CompletableFuture ▸Other features ▸Dark side of Java 8 ▸Conclusion
- 56. CONCLUSION ▸ Anonymous class- lambdas ▸ Database-like routines - Stream API ▸ Get to know functional programming ▸ Null pointer exception - Optional ▸ Lots of syntactic sugar in collections method
- 57.