1. Lambda expressions 2. Streams API 3. Changes in interfaces 4. Nashorn 5. Optional 6. Java time 7. Accumulators

1. Getting ready
to Java 8
Sergey Morenets, morenets@mail.ru
24 July 2014 г.

2. About author
• Works in IT since 2000
• 11 year of Java SE/EE experience
• Occupied senior Java developer/Team Lead
positions
• Winner of 2013 JBoss Community Recognition
Award. https://www.jboss.org/jbcra

3. About author
• 6 times speaker at Odessa Java User Group
• 2 times speaker at JEEConf (2013 and 2014) in Kiev
• Speaker at Java Breeze 2013 in Odessa
• Speaker at Java Day 2014 in Minsk
• Works 2 years as Java lector

4. Java 8
• Java 8 has been influenced by Scala much more
than how Scala has been influenced by Java
• Most expected Java release ever

5. JVM-based languages

6. Functional languages

7. Java 8
• Code name Kenai
• Specification JSR-337
• Inspired by Scala, Google Guava and Joda Time

8. Java 8
• Project Lambda
• Streams API
• Functional interfaces
• Java time
• Method references
• Repeatable & time annotations
• Nashorn
• Accumulators

9. Java 8
• Method Thread.stop() was deprecated in 1998 and
rewritten to throw exception in 2014.

10. Schedule
• 2012/04/26 M1
• 2012/06/14 M2
• 2012/08/02 M3
• 2012/09/13 M4
• 2012/11/29 M5
• 2013/01/31 M6
• 2013/06/13 Feature Complete
• 2013/09/05 Developer Preview
• 2014/01/23 Final Release Candidate
• 2014/03/18 General Availability

11. Java 7

12. Java 7

13. Project Lambda

14. Project Lambda

15. Project Lambda

16. Java 7

17. Project Lambda

18. Project Lambda

19. Java 7

20. Project Lambda

21. Project Lambda

22. Project Lambda
• Lambdas are not serializable
• Applied to functional interfaces(with SAM)
• Cannot use this
• Not applied to abstract classes(even with SAM)

23. Project Lambda
• Function
• Predicate
• Consumer
• Supplier
• BinaryOperator

24. Project Lambda
Interface Description
Function Function with single
argument and result
Predicate Tests condition of single
argument
Consumer Performs operation over
single argument
Supplier Supplies results
BinaryOperator Functions with two
arguments and results

25. Lambda vs Anonymous

26. Lambda vs Anonymous

27. Lambda vs Anonymous

28. Lambda vs Anonymous
Type Lambdas(ms) Anonymous classes (ms)
Execution 364 329
Capturing 316 309
Linkage 354 313

29. Disadvantage

30. Java 7

31. Method reference

32. Method reference

33. Java 7

34. Streams

35. Streams

36. Streams

37. Streams

38. Java 7

39. Streams

40. Streams
• Sequential
• Parallel

41. Streams

42. Performance

43. Performance
Operation Sequential, sec Parallel,sec
Slow operation 1.0 0.4
Quick operation 0.3 2.4

44. Parallelism level

45. Parallelism level
• Parallel streams use ForkJoinPool to split and
combine tasks
• By default number of threads is equal to number of
processors
• This behavior may be overridden by changing
system property
java.util.concurrent.ForkJoinPool.common.parallelism

46. Streams

47. Streams

48. Streams

49. Streams

50. Java 7

51. Streams

52. Stream performance

53. Stream performance

54. Iteration test
Use case Time(ms)
For-each loop 35
forEach(lambda) 79
forEach(consumer) 12

55. Java 7

56. Default methods

57. Default methods

58. Default methods

59. Default methods
• equals
• hashCode
• toString

60. Java 7

61. Java 7

62. Java 7

63. Optional

64. Optional

65. Optional

66. Construct date

67. Java 7

68. Java Time

69. Java Time

70. Java Time

71. Java Time

72. Java 7

73. Java Time

74. Time difference

75. Java Time

76. I/O

77. I/O

78. Encoding

79. Annotations

80. Annotations

81. Repeatable annotations

82. Repeatable annotations

83. Repeatable annotations

84. Annotations
• Up to Java 7, an annotation was applied to a
declaration.
• A declaration is a part of code that introduces a
new name.

85. Annotations
• Type
• Method
• Field
• Annotation
• Package
• Local variable

86. Type annotations

87. Type annotations
• In Java 8, you can annotate any type use.
• This can be useful in combination with tools that
check for common programming errors

88. Type annotations

89. Type annotations
• Generic type arguments
• Superclass and implemented interface
• Constructor invocations
• Casting and instanceof
• Exception specifications
• Wild card and type bounds

90. Type annotations

91. Nashorn

92. Nashorn
• Based on Da Vinci Machine
• Intends to enable Java developers embedding of
JavaScript in Java applications
• Successor of JavaScript Rhino engine which was
started in 1997 by Netscape and maintained by
Mozilla.

93. Java 7

94. Nashorn

95. Performance
Operation Rhino(Java 7) ,sec Nashorn (Java 8)
print 3.1 0.9
String operations 1.0 0.4
Math operations 1.4 0.1

96. Collections
• Improved HashMap
• Balanced tree to avoid high collisions

97. Collections

98. Collections

99. Performance
Number of items Java 7,ms Java 8
1000 7 9
5000 67 47
15000 653 406
30000 2645 1252
50000 7842 3820

100. Accumulators
• Scalable updatable variables. Maintaining a single
count, sum, etc., that is updated by possibly many
threads is a common scalability problem.
• Added features that make ConcurrentHashMap
and classes built from them more useful as caches.
Better support for maps with large numbers of
elements.
• Added functionality and improved performance for
ForkJoinPool

101. Benchmark

102. Benchmark

103. Benchmark

104. Benchmark
Number of threads AtomicLong LongAdder
1 236 177
2 586 138
4 590 46
8 501 49
16 438 48
32 459 52

105. Metaspace
• Replacement of Permanent Generation
• New JVM arguments
• Resides in the heap and can be resized

106. Q&A
• Сергей Моренец, morenets@mail.ru