Whats New in Java 8
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This document summarizes some of the new features introduced in Java 8, including streams, lambda expressions, default methods, and date/time API changes. It discusses streams in more detail, covering stream operations like filter, map, distinct, and collect. It also covers new features like Optional for returning absent/present values, annotations for null checks, parallel array sorting, and concurrency utilities.
![Stream notes: Short circuiting
Random random = new Random();
int[] result = IntStream
.generate(() ->random.nextInt())
.sorted()
.toArray();](https://image.slidesharecdn.com/jug-presentation-140508151219-phpapp01/85/Whats-New-in-Java-8-18-320.jpg)
![Stream notes: not reusable
IntStream stream = Arrays.stream(new int[]{1, 2, 3, 4});
List<Object> list = stream.boxed().collect(Collectors.toList());
// this throws java.lang.IllegalStateException
double average = stream.average().getAsDouble();](https://image.slidesharecdn.com/jug-presentation-140508151219-phpapp01/85/Whats-New-in-Java-8-21-320.jpg)
![Checker framework
• @Interned String intern() { ... } // return value
• int compareTo(@NonNull String other) { ... } // parameter
• String toString(@ReadOnly MyClass this) { ... } // receiver
• @NonNull List<@Interned String> messages; // generics: non-
null list of interned Strings
• @Interned String @NonNull [] messages; // arrays: non-null
array of interned Strings
• myDate = (@ReadOnly Date) readonlyObject; // cast](https://image.slidesharecdn.com/jug-presentation-140508151219-phpapp01/85/Whats-New-in-Java-8-30-320.jpg)
Whats New in Java 8
- 1. What’s new in Java 8 Maxim Zakharenkov 3 April, 2014
- 2. Existing presentations • Новое в JDK 8. Александр Ильин, Oracle https://www.youtube.com/watch?v=lSnNWRABA1s • JDK8: Stream style, Sergey Kuksenko, Oracle http://www.slideshare.net/SergeyKuksenko/jdk8-stream-style • More on slideshare
- 3. What this talk is about • Streams • Stream notes • Some other new features in Java 8 – Optional<?> – Annotations – parallelSort – Concurrency – Some other stuff
- 13. filter()
- 14. filter() map()
- 18. Stream notes: Short circuiting Random random = new Random(); int[] result = IntStream .generate(() ->random.nextInt()) .sorted() .toArray();
- 19. Stream notes: parallel forEach DEMO
- 20. Stream notes: parallel forEach • forEach does not preserve order! • Use forEachOrdered if order matters
- 21. Stream notes: not reusable IntStream stream = Arrays.stream(new int[]{1, 2, 3, 4}); List<Object> list = stream.boxed().collect(Collectors.toList()); // this throws java.lang.IllegalStateException double average = stream.average().getAsDouble();
- 22. Optional results 1 public String findById(int id) { // ... return …; }
- 23. Optional results 2 public String findById(int id) { // ... return …; } String result = findById(10);
- 24. Optional results 3 public String findById(int id) { // ... return …; } String result = findById(10); prefix = result.substring(0, 3);
- 25. Optional results 4 public String findById(int id) { // ... return …; } String result = findById(10); if(result != null) { prefix = result.substring(0, 3); }
- 26. Optional results 5 public String ? findById(int id) { // ... return …; } String result = findById(10); prefix = result.substring(0, 3);
- 27. Optional results 6 public Optional<String> findById(int id) { // ... return …; } if(result.isPresent()) { }
- 28. Annotations public @NonNull String findById(int id) { // ... return …; }
- 30. Checker framework • @Interned String intern() { ... } // return value • int compareTo(@NonNull String other) { ... } // parameter • String toString(@ReadOnly MyClass this) { ... } // receiver • @NonNull List<@Interned String> messages; // generics: non- null list of interned Strings • @Interned String @NonNull [] messages; // arrays: non-null array of interned Strings • myDate = (@ReadOnly Date) readonlyObject; // cast
- 31. Arrays.parallelSort • Works faster • Everyting has own cost – DualPivotQuickSort - sequental – MergeSort - parallel
- 32. Parallel sort of 50M elements (on my 4 core laptop) • Single threaded DualPivotQuickSort: 47sec • Parallel merge sort: 21sec • Sequential stream: 95sec • Parallel stream: 104sec
- 33. Parallelism, is it good or bad? (example) • 2 CPU • Concurrent clients - 1000 queries per second • Single sequential sort - 2ms • Single parallel sort - 1ms + sync overhead ~1.2ms • Less transactions per second with parallel sort • Parallel algorithms do not always fit well
- 35. HashMap before Java 8 0 key1 1 2 3 4 5 6 key2 key3 key4 key4
- 36. HashMap in Java 8 0 key1 1 2 3 4 5 6 key2 key3 key4 key4
- 37. MissionControl • Cool tool for JVM diagnostics • Comes with JDK installation (jmc executable • Now we have 3 similar tools in JDK – jconsole – jvisualvm – jms
- 38. Future of frameworks • Type-safe property references in Hibernate- like query languages • JUnit, Mockito-like frameworks with method references • Event handlers • Better XML and JSON serializers • - ….
- 39. QA