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Java8 training - class 3
The document covers Java 8 training focused on stream operations, including intermediate methods (filter, map) and terminal operations, alongside new features like the DateTime API and Optional class. It illustrates examples of processing lists using streams and highlights the differences between traditional IO and NIO in Java. Additionally, it discusses parallel processing and lazy evaluation in streams.
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Java8 training - class 3
- 1. Java8 Training –Class 3 -Marut Singh Email: singh.marut@gmail.com https://github.com/singhmarut/java8training http://www.Marutsingh.com http://www.marutsingh.com
- 2. Stream Operations Intermediate Lazy Always create a new stream Stateless (filter, map) Stateful (distinct,sorted) Terminal http://www.marutsingh.com
- 3. Stream Operations forEach Randomrandom = new Random(); random.ints().limit(10).forEach(System.out::println); map List<Integer> numbers = Arrays.asList(3, 2, 2, 3, 7, 3, 5); //get list of unique squares List<Integer> squaresList = numbers.stream() .map( i -> i*i).distinct().collect(Collectors.toList()); filter List<String>strings = Arrays.asList("abc", "", "bc", "efg", "abcd","", "jkl"); //get count of empty string int count = strings.stream().filter(string -> string.isEmpty()).count(); http://www.marutsingh.com
- 4. Stream operations sorted Randomrandom = new Random(); random.ints().limit(10).sorted().forEach(System.out::println); Distinct Parallel Processing List<String> strings = Arrays.asList("abc", "", "bc", "efg", "abcd","", "jkl"); //get count of empty string int count = strings.parallelStream().filter(string -> string.isEmpty()).count(); Collectors List<String>strings = Arrays.asList("abc", "", "bc", "efg", "abcd","", "jkl"); List<String> filtered = strings.stream().filter(string -> !string.isEmpty()).collect(Collectors.toList()); System.out.println("Filtered List: " + filtered); String mergedString = strings.stream().filter(string -> !string.isEmpty()).collect(Collectors.joining(", ")); System.out.println("Merged String: " + mergedString); http://www.marutsingh.com
- 5. Statistics Arrays.asList(3, 2,2, 3, 7, 3, 5) .stream().mapToInt((x) -> x).getMax(); http://www.marutsingh.com
- 6. Optional Class AvoidNullPointerException Optional.empty() Optional.of(Class<T>) Optional.ofNullable(Class<T>) http://www.marutsingh.com
- 7. Lazy Processing Bydefault all intermediate operations are lazy They all return Stream<T> http://www.marutsingh.com
- 8. Sorting a stream new Random().ints().limit(10).sorted().forEach(rand -> System.out.println(rand)); http://www.marutsingh.com
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- 10. Parallel Streams behavioralparameters in stream pipelines whose source might not be concurrent should never modify the stream's data source. A behavioral parameter is said to interfere with a non-concurrent data source if it modifies, or causes to be modified, the stream's data source. http://www.marutsingh.com
- 11. New DateTime API Problems with old date time api (java.util.date) Not thread safe Inconsistent design Default Date starts from 1900 (month starts from 1, and day starts from 0) Difficult time zone handling http://www.marutsingh.com
- 12. Java.time Classes Local− Simplified date-time API with no complexity of timezone handling via static methods LocalDate LocalTime LocalDateTime Instant (Instant is an instantaneous point on the global time-line (UTC), and is unrelated to time-zone) Zoned - Specialized date-time API to deal with various timezones. Periods - deal with date based amount of time. Duration - deal with time based amount of time. http://www.marutsingh.com
- 13. Java.time ZoneId ireland= ZoneId.ofOffset("GMT", ZoneOffset.ofHours(+3)); http://www.marutsingh.com
- 14. File NIO MainDifferences Betwen Java NIO and IO http://www.marutsingh.com IO NIO Stream oriented Buffer oriented Blocking IO Non blocking IO Selectors