1

Get ready for moving from Java 6 to Java 8 – Now!

René Winkelmeyer 24.03.2016

2

•  Skype / Twitter / LinkedIn / Slideshare

muenzpraeger

•  Web https://blog.winkelmeyer.com

•  Mail mail@winkelmeyer.com

OpenNTF •  File Navigator •  Generic NSF View Widget for IBM Connections

About me

René Winkelmeyer Head of Development

3

YES – I CAN!

4

A timeline perspective

§  Quick poll

§  IBM Notes/Domino development?

§  WebSphere development?

§  Java 6 only development?

§  Java 7+ only development?

§  Mixed Java version development?

5

A timeline perspective

6

A timeline perspective

Java 6 23.12.2006

Java 7 28.07.2011

Java 8 18.03.2014

Java 9 23.03.2017

Java versions by release date

IBM Notes/Domino

IBM WebSphere (Full Profile)

IBM WebSphere (Liberty Profile)

Supported Java

version by product

7

What this session covers

§  Switch-strings

§  Diamonds

§  Paths

§  Lambdas

§  Streams

§  Date/Time

8

Goodbye if-then-elseif-elseif-elseif… for Strings

9

Goodbye if-then-elseif-elseif-elseif… for Strings

Way in Java 6 and smaller to check for different String types

10

Goodbye if-then-elseif-elseif-elseif… for Strings

§  Java 7 added support for java.lang.String in switch

§  Increased readability

§  Produces more efficient byte code

§  Switching based on the hashcode()

§  May (still) throw a NullPointerException

11

Goodbye if-then-elseif-elseif-elseif… for Strings

Now a clean way. Alternative could be to use Enums (also prior Java 7).

12

Diamonds are developers best friends

13

Diamonds are developers best friend

§  Java 7 introduced the usage of the <> operator for type inference

§  Removes verbose code

§  Makes usage of 3rd party libs like Google Guava for List creation obsolete

14

Diamonds are developers best friend

Raw error warning in Eclipse. Technically possible, but not recommended.

How to do it. Imagine HashMap<String, HashMap<String, Object>> i. e.

Diamond operator for less code writing. ;-)

15

Automated resource management

16

Automated resource management (simple)

Close in finally

Multiple exceptions to catch

Init outside the try to close it later

17

Automated resource management

§  Java 7 introduced the new java.lang.AutoCloseable interface

§  Resources that inherit from this interface are automatically closed when created within a try statement

§  Reduces boilerplate code drastically

§  java.lang.Closeable extends from java.lang.AutoCloseable

§  AutoCloseable.close() shouldn‘t be called twice!

18

Automated resource management (simple)

Close in finally

Multiple exceptions to catch

Init outside the try to close it later

19

Automated resource management (simple)

No finally, no close()

20

Automated resource management (more)

Multiple streams to close

Multiple streams to handle

Multiple streams to close

21

Automated resource management (more)

„Join“ multiple AutoCloseables with a ; separator within the try statement

22

Underscore me

23

Underscore me

§  You‘ve two seconds to identify these numbers

24

Underscore me

§  The with Java 7 introduced capability allows to add underscores to numeric types (int, double, long).

§  A few rules to obey:

§  Can be used after the decimal point, but not directly before/after it

§  No underscores at the end or the beginning (i. e. _5000 or 5000_)

25

Underscore me

§  You‘ve two seconds to identify these numbers

26

Underscore me

§  You‘ve two seconds to identify these n_e_w numbers

27

Catch me if you can

28

Catch me if you can

One catch per named exception

29

Catch me if you can

multi-catch has been introduced with Java 7

30

NIO.2

31

NIO.2

§  The handling of file system related actions has been much improved with Java 7.

§  Removes the need in a lot of cases to rely on 3rd pary libraries like Apache Commons Files.

§  Direct implementation in the base JDK

32

NIO.2

§  java.nio.Path

§  Think of it as a replacement for java.io.File

§  Represents a file or a folder – and it doesn‘t need to exist (no Exception ;-))

§  java.nio.Files

§  Loads of utility classes for file and folder handling

33

Make your Path (and more)

34

Make your Path (and more)

35

Watch your files

Initiates the default WatchService as introduced with Java 7

Assign the to be monitored path using the new java.nio.Path API

Register the created WatchService with the path. Events that can be monitored are create, update and delete.

36

Watch your files

Holds the results of the monitored events

Map of all found events

37

default

38

default

§  Changes in Interfaces always led to changes in the classes they used them

§  The new default constructor introduces „backward“ compatibility

39

Before Java 8

40

Before Java 8

Adding a new Interface method

Compilation error on all classes that implement the Interface

41

With Java 8

Method body needed

42

With Java 8

Calling a duplicate default method

43

Lambdas

44

Lambdas

§  One of the biggest changes with Java 8

§  Known from other languages like Closure, Scala, C# and more

§  Defined in Java Specification Request (JSR) 335

§  Knows as closures or functional literals in other languages

§  Love or hate them – there‘s no way around them!

45

Lambdas

Standard boilerplate code to iterate Sequential, not parallel!

46

Lambdas

Anonymous methods to the rescue but ...

Have you spotted the forEach?

47

Lambdas

Calling the anonymous inner method directly via a lambda call

48

Lambdas

Shorten it even more by omitting the casting

49

Lambdas

50

Lambdas

51

Streams

52

What is a stream and what not?

§  It is a pipeline of functions that can be evaluated.

§  They are not a data structure.

§  They can transform data – but cannot mutate them.

53

Available stream functions

Source:http://zeroturnaround.com/rebellabs/java-8-streams-cheat-sheet/attachment/java-8-streams-cheat-sheet-v3/

54

Streams

Calling the stream

Termination call

55

Streams and Lambdas

Much cleaner implementation using Streams and Lambdas

Obey the new lines – better for debugging...

56

Streams – a little bit more complete

Output: C1 C2

57

Streams – a little bit more complete

Source:http://zeroturnaround.com/rebellabs/java-8-streams-cheat-sheet/attachment/java-8-streams-cheat-sheet-v3/

58

Date and Time

59

Date and Time

§  Who loves Date and Time operations in Java?

§  Who is using Joda Time?

60

Date and Time – Spot the error

+1900 0-based

61

Date and Time – Basic Concept

§  LocalDate, LocalTime, LocalDateTime

§  Instant (amount of time since the epoch, i. e. for timestamps)

§  Period

§  Duration

62

Date and Time – Examples

§  Now -> LocalDate.now()

§  Static -> LocalDate(2013, Month.JANUARY, 21)

§  Parse -> LocalDate.parse()

§  Conversion -> Calendar.getInstance().toInstant()

63

Date and Time – Examples

64

Date and Time – Examples

65

Q & A!