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Java 8 Lambda Expressions
The document discusses the use of Java 8 lambda expressions, highlighting their advantages such as promoting immutability, easier parallelization, and writing cleaner code. It provides various examples of utilizing lambda expressions for iterating, filtering, and reducing data structures, specifically focusing on lists. Additionally, it includes resources and contact information for further exploration of the topic.
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Java 8 Lambda Expressions
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- 2. Mom, why? Promote immutability Declarewhat to do, not how to do it Easier parallelization & lazy evaluation Cleaner, more concise code
- 3. List<Integer> numbers = Arrays.asList(1,2, 3, 4, 5, 6, 7, 8, 9, 10); numbers.forEach(new Consumer<Integer>() { @Override public void accept(Integer integer) { System.out.println(integer); } }); iterating w/ forEach (under the hood)
- 4. lambda expressions (argument list)-> code (final String name, final int age) -> code (name, age) -> code name -> code examples: type inference (String name, int age) -> code } λ
- 5. iterating w/lambdas List<Integer> numbers= Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10); numbers.forEach((final Integer value) -> System.out.println(value)); lambda expression
- 6. iterating w/lambdas, typeinference List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10); numbers.forEach(value -> System.out.println(value));
- 7. method references List<Integer> numbers= Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10); numbers.forEach(System.out::println); method reference
- 8. transforms using map List<Integer>numbers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10); numbers.stream() .map(value -> value * 2) .forEach(System.out::println);
- 9. filtering List<Integer> numbers = Arrays.asList(1,2, 3, 4, 5, 6, 7, 8, 9, 10); numbers.stream() .filter(value -> value % 2 == 0) .forEach(System.out::println);
- 10. filtering v2 List<String> names= Arrays.asList( "Bob", "Tom", "Jeff", "Scott", "Jennifer", "Steve"); final Function<String, Predicate<String>> startsWithLetter = letter -> name -> name.startsWith(letter); names.stream() .filter(startsWithLetter.apply("J")) .forEach(System.out::println);
- 11. Streams.iterate(1, number ->number + 1) .map(number -> number * number) .limit(25) .forEach(number -> System.out.print(number + " ")); // 1 4 9 16 25 36 49 64 ... 529 576 625 Streams
- 12. finding with Optional List<String>names = Arrays.asList( "Bob", "Tom", "Jeff", "Scott", "Jennifer", "Steve"); Optional<String> firstS = names.stream() .filter(name -> name.startsWith("S")) .findFirst(); System.out.println(firstS.orElse("None found"));
- 13. reducers List<String> names =Arrays.asList( "Bob", "Tom", "Jeff", "Scott", "Jennifer", "Steve"); Optional<String> longestName = names.stream() .reduce((name1, name2) -> name1.length() >= name2.length() ? name1 : name2); if (longestName.isPresent()) { System.out.println(longestName.get()); }
- 14. sum reducer List<Integer> numbers= Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10); long sum = numbers.stream() .map(value -> value * value) .sum();
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- 16. how far wewent in this short talk...
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- 19. sample code availableat: https://github.com/sleberknight/java8-lambda-samples
- 20. My Info scott dotleberknight at nearinfinity dot com twitter.com/sleberknight www.sleberknight.com/blog www.nearinfinity.com/blogs/scott_leberknight/all/ scott dot leberknight at gmail dot com