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![$ cat limerick.txt | tr -cs "[:alpha:]" "n" | awk '{print
length(), $0}' | sort | uniq
1 a
2 as
2 of
2 on
3 And
3 Who
3 she
3 the
3 was
4 They
4 With
4 face
4 from
4 lady
4 ride
4 rode
5 Niger
5 There
5 smile
5 tiger
5 young
6 inside
6 smiled
8 returned](https://image.slidesharecdn.com/sailingwithjava8streams-160401091838/75/Sailing-with-Java-8-Streams-16-2048.jpg)
![public static void main(String []file) throws Exception {
// process each file passed as argument
// try opening the file with FileReader
try (FileReader inputFile = new FileReader(file[0])) {
int ch = 0;
while( (ch = inputFile.read()) != -1) {
// ch is of type int - convert it back to char
System.out.print( (char)ch );
}
}
// try-with-resources will automatically release FileReader object
}
public static void main(String []file) throws Exception {
Files.lines(Paths.get(file[0])).forEach(System.out::println);
}
Existing APIs are enriched with
lambdas and streams support](https://image.slidesharecdn.com/sailingwithjava8streams-160401091838/75/Sailing-with-Java-8-Streams-19-2048.jpg)
![interface LambdaFunction {
void call();
}
class FirstLambda {
public static void main(String []args) {
LambdaFunction lambdaFunction = () -> System.out.println("Hello world");
lambdaFunction.call();
}
}
Functional interface - provides
signature for lambda functions
Lambda function/expression
Call to the lambda
Prints “Hello world” on the console when executed](https://image.slidesharecdn.com/sailingwithjava8streams-160401091838/75/Sailing-with-Java-8-Streams-21-2048.jpg)
![Method[] objectMethods = Object.class.getMethods();
Stream<Method> objectMethodStream = Arrays.stream(objectMethods);
Stream<String> objectMethodNames
= objectMethodStream.map(method -> method.getName());
Stream<String> uniqueObjectMethodNames = objectMethodNames.distinct();
uniqueObjectMethodNames.forEach(System.out::println);
Arrays.stream(Object.class.getMethods())
.map(method -> method.getName())
.distinct()
.forEach(System.out::println);
Breaking up into separate
(looong) statements for our
understanding](https://image.slidesharecdn.com/sailingwithjava8streams-160401091838/75/Sailing-with-Java-8-Streams-27-2048.jpg)
![import java.util.Arrays;
class StringConcatenator {
public static String result = "";
public static void concatStr(String str) {
result = result + " " + str;
}
}
class StringSplitAndConcatenate {
public static void main(String []args) {
String words[] = "the quick brown fox jumps over the lazy dog".split(" ");
Arrays.stream(words).forEach(StringConcatenator::concatStr);
System.out.println(StringConcatenator.result);
}
}
Gives wrong results with
with parallel() call](https://image.slidesharecdn.com/sailingwithjava8streams-160401091838/75/Sailing-with-Java-8-Streams-56-2048.jpg)
Uploaded byGanesh Samarthyam
Sailing with Java 8 Streams
The document discusses Java 8 streams and lambda expressions, showcasing their ability to simplify functional programming in Java. It includes examples of how to use streams for data processing and emphasizes the advantages of internal iteration over traditional external iteration methods. The content highlights the efficiency of using parallel streams for performance improvements in computations.
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Sailing with Java 8 Streams
- 1. SAILING WITH JAVA8 STREAMS ocpjava.wordpress.com Ganesh Samarthyam
- 2.
- 3. Java 8: Latest(red-hot)
- 4.
- 5.
- 6. He he, butlambdas are fun, not scary
- 7. Java meets functional programming(with lambdas)
- 8. Introducing our star feature- lambda functions
- 9. List<String> strings =Arrays.asList("eeny", "meeny", "miny", "mo"); Consumer<String> printString = string -> System.out.println(string); strings.forEach(printString); Lambda functions!
- 10.
- 11. Lambdas is justa fancy name for functions without a name!
- 12. Arrays.asList("eeny", "meeny", "miny",“mo”) .forEach(string -> System.out.println(string)); Internal Iteration List<String> strings = Arrays.asList("eeny", "meeny", "miny", "mo"); for(String string : strings) { System.out.println(string); } External Iteration Lambda expression
- 13. You can uselambdas for some amazing stuff
- 14. sediment pre- carbon ultra-filter post- carbon Filtered water E.g., you cancompose lambda functions as in pipes-and-filters
- 15. $ cat limerick.txt Therewas a young lady of Niger Who smiled as she rode on a tiger. They returned from the ride With the lady inside And a smile on the face of the tiger.
- 16. $ cat limerick.txt| tr -cs "[:alpha:]" "n" | awk '{print length(), $0}' | sort | uniq 1 a 2 as 2 of 2 on 3 And 3 Who 3 she 3 the 3 was 4 They 4 With 4 face 4 from 4 lady 4 ride 4 rode 5 Niger 5 There 5 smile 5 tiger 5 young 6 inside 6 smiled 8 returned
- 17. List<String> lines = Files.readAllLines(Paths.get("./limerick.txt"),Charset.defaultCharset()); Map<Integer, List<String>> wordGroups = lines.stream() .map(line -> line.replaceAll("W", "n").split("n")) .flatMap(Arrays::stream) .sorted() .distinct() .collect(Collectors.groupingBy(String::length)); wordGroups.forEach( (count, words) -> { words.forEach(word -> System.out.printf("%d %s %n", count, word)); }); 1 a 2 as 2 of 2 on 3 And 3 Who 3 she 3 the 3 was 4 They 4 With 4 face 4 from 4 lady 4 ride 4 rode 5 Niger 5 There 5 smile 5 tiger 5 young 6 inside 6 smiled 8 returned
- 18. Lambdas & streamshelp in productive programming!
- 19. public static voidmain(String []file) throws Exception { // process each file passed as argument // try opening the file with FileReader try (FileReader inputFile = new FileReader(file[0])) { int ch = 0; while( (ch = inputFile.read()) != -1) { // ch is of type int - convert it back to char System.out.print( (char)ch ); } } // try-with-resources will automatically release FileReader object } public static void main(String []file) throws Exception { Files.lines(Paths.get(file[0])).forEach(System.out::println); } Existing APIs are enriched with lambdas and streams support
- 20. So, lets getour hands dirty and start coding
- 21. interface LambdaFunction { voidcall(); } class FirstLambda { public static void main(String []args) { LambdaFunction lambdaFunction = () -> System.out.println("Hello world"); lambdaFunction.call(); } } Functional interface - provides signature for lambda functions Lambda function/expression Call to the lambda Prints “Hello world” on the console when executed
- 22. @FunctionalInterface interface LambdaFunction { voidcall(); } Functional interface Abstract method providing the signature of the lambda function Annotation to explicitly state that it is a functional interface
- 23. arg -> System.out.println(arg) System.out::println Methodreferences - “syntactic sugar” for lambda functions They “route” function parameters
- 24. Java 8 streams(and parallel streams): Excellent example of applying functional programming in practice
- 25. But what arestreams?
- 26.
- 27. Method[] objectMethods =Object.class.getMethods(); Stream<Method> objectMethodStream = Arrays.stream(objectMethods); Stream<String> objectMethodNames = objectMethodStream.map(method -> method.getName()); Stream<String> uniqueObjectMethodNames = objectMethodNames.distinct(); uniqueObjectMethodNames.forEach(System.out::println); Arrays.stream(Object.class.getMethods()) .map(method -> method.getName()) .distinct() .forEach(System.out::println); Breaking up into separate (looong) statements for our understanding
- 28.
- 29.
- 30. IntStream.range(1, 6) You canuse range or iterate factory methods in the IntStream interface IntStream.iterate(1, i -> i + 1).limit(5)
- 31. 1 2 3 4 5 1 4 9 16 25 map(i -> i * i) IntStream.range(1, 5).map(i -> i * i).forEach(System.out::println); Using streams instead of imperative for i = 1 to 5, print i * i
- 32. Stream.of (1, 2,3, 4, 5) .map(i -> i * i) .peek(i -> System.out.printf("%d ", i)) .count(); prints: 1 4 9 16 25
- 33. stream can be infinite IntStream.iterate(0,i -> i + 2).forEach(System.out::println); This code creates infinite stream of even numbers!
- 34. IntStream .iterate(0, i ->i + 2) .limit(5) .forEach(System.out::println); Using the “limit” function to limit the stream to 5 integers
- 35. IntStream chars ="bookkeep".chars(); System.out.println(chars.count()); chars.distinct().sorted().forEach(ch -> System.out.printf("%c ", ch)); Cannot “reuse” a stream; this code throws IllegalStateException
- 36.
- 37. Files.lines(Paths.get("FileRead.java")).forEach(System.out::println); This code printsthe contents of the file “FileRead.java” in the current directory
- 38. Pattern.compile(" ").splitAsStream("java 8streams").forEach(System.out::println); This code splits the input string “java 8 streams” based on whitespace and hence prints the strings “java”, “8”, and “streams” on the console
- 39. new Random().ints().limit(5).forEach(System.out::println); Generates 5random integers and prints them on the console
- 40. "hello".chars().sorted().forEach(ch -> System.out.printf("%c", ch)); Extracts characters in the string “hello”, sorts the chars and prints the chars
- 41.
- 42.
- 44.
- 46. I really reallyhate concurrency problems
- 47.
- 48. Sometimes, dreams docome true even at 86 :-)
- 49. So, keep dreamingtill you become 86!
- 50. long numOfPrimes =LongStream.rangeClosed(2, 100_000) .filter(PrimeNumbers::isPrime) .count(); System.out.println(numOfPrimes); Prints 9592 2.510 seconds
- 51. Parallel code Serial code Let’sflip the switch by calling parallel() function
- 52. long numOfPrimes =LongStream.rangeClosed(2, 100_000) .parallel() .filter(PrimeNumbers::isPrime) .count(); System.out.println(numOfPrimes); Prints 9592 1.235 seconds
- 53. Wow! That’s anawesome flip switch!
- 54. Internally, parallel streamsmake use of fork-join framework
- 56. import java.util.Arrays; class StringConcatenator{ public static String result = ""; public static void concatStr(String str) { result = result + " " + str; } } class StringSplitAndConcatenate { public static void main(String []args) { String words[] = "the quick brown fox jumps over the lazy dog".split(" "); Arrays.stream(words).forEach(StringConcatenator::concatStr); System.out.println(StringConcatenator.result); } } Gives wrong results with with parallel() call
- 57.
- 58. ❖ Programming examplesare from our book: ❖ Oracle Certified Professional Java SE 8 Programmer Exam 1Z0-809: A Comprehensive OCPJP 8 Certification Guide, S.G. Ganesh, Hari Kiran Kumar, Tushar Sharma, Apress, 2016. ❖ Website: ocpjava.wordpress.com
- 59. Image credits • http://www.wetplanetwhitewater.com/images/uploads/adam_mills_elliott82.jpg •http://s.ecrater.com/stores/321182/53e46c705f68d_321182b.jpg • http://img.viralpatel.net/2014/01/java-lambda-expression.png • https://i.ytimg.com/vi/3C0R_fEXcYA/maxresdefault.jpg • http://farm1.static.flickr.com/74/170765090_53762a686c.jpg • http://www.monazu.com/wp-content/uploads/2012/06/ask-the-right-questions.jpg • https://s-media-cache-ak0.pinimg.com/736x/43/42/8a/43428ac2c352166374d851e895ed5db1.jpg • http://cdn.attackofthecute.com/August-17-2011-12-36-23-peekaboo- kitty-46f32anul-131384-530-410.jpeg • https://ludchurchmyblog.files.wordpress.com/2010/02/myths-legend-pictures-083.jpg • http://www.youramazingplaces.com/wp-content/uploads/2013/06/Mauvoisin-Dam- Switzerland-620x413.jpg • http://www.welikeviral.com/files/2014/08/Image-914.jpg • http://geekandpoke.typepad.com/.a/6a00d8341d3df553ef013485f6be4d970c-800wi • https://qph.fs.quoracdn.net/main-qimg-56547c0506050206b50b80a268bf2a84 • https://i.ytimg.com/vi/kCVsKsgVhBA/maxresdefault.jpg • http://i.livescience.com/images/i/000/022/395/original/man-dreams-bed.jpg • https://static-secure.guim.co.uk/sys-images/Guardian/Pix/pictures/2012/11/26/1353952826063/Alarm- clock-010.jpg
- 60. email sgganesh@gmail.com website www.designsmells.com twitter@GSamarthyam linkedin bit.ly/sgganesh slideshare slideshare.net/sgganesh