Java 8 - Lambdas and much more
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The presentation introduces several new features in Java 8 including lambdas, default methods, streams API, and method references. Lambdas allow for anonymous functions and simplify implementing interfaces with single methods. Default methods allow interfaces to define implementations while maintaining backwards compatibility. The streams API provides a functional-style way to process collections through filtering, mapping, matching, and reducing operations. Method references allow referring to methods without anonymous classes.
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Java 8 - Lambdas and much more
- 1. Java 8 Lambdas and much more Alin Pandichi @alinpandichi
- 2. About me (Not only Java) software developer Professional experience of 5 years BJUG and AgileWorks community member Twitter: @alinpandichi
- 3. We’ll talk about Lambdas Default methods Streams Method references
- 4. Java 8 Expected on 18 March 2014 Lambdas: one of the most anticipated features Remember 'Plan B for Java 7'?
- 5. Play with it https://github.com/AdoptOpenJDK/lambda-tutorial https://jdk8.java.net/lambda/ IDE support: http://www.jetbrains.com/idea/download/ http://wiki.eclipse.org/JDT/Eclipse_Java_8_Support_(BETA) http://bits.netbeans.org/dev/nightly/latest/
- 7. External iteration vs. Internal iteration List<Shape> shapes = /* ... */; for (Shape shape :shapes) { shape.setColor(newColor); } shapes.forEach(shape -> shape.setColor(newColor));
- 9. Lambda () -> {} (s) -> { System.out.println(s) }
- 10. Lambda () -> {} (s) -> { System.out.println(s) } s -> System.out.println(s)
- 11. Lambda (x, y) -> { return x + y; }
- 12. Lambda (x, y) -> { return x + y; } (x, y) -> x + y
- 13. Lambda (x, y) -> { return x + y; }
- 14. Lambda Adder adder = (x, y) -> { return x + y; };
- 15. Lambda Adder adder = (x, y) -> { return x + y; }; public interface Adder { public int adder(int x, int y); }
- 16. Lambda Adder adder = (x, y) -> { return x + y; }; @FunctionalInterface public interface Adder { public int adder(int x, int y); }
- 17. Lambda Adder adder = (x, y) -> { return x + y; }; Adder adder = new Adder() { @Override public int add(int x, int y) { return x + y; } };
- 18. Iterable.forEach public interface Iterable<T> { Iterator<T> iterator(); }
- 19. Iterable.forEach public interface Iterable<T> { Iterator<T> iterator(); void forEach(Consumer<? super T> action); }
- 20. Iterable.forEach public interface Iterable<T> { Iterator<T> iterator(); void forEach(Consumer<? super T> action); } Could break 99% of existing codebases!
- 21. Iterable.forEach public interface Iterable<T> { Iterator<T> iterator(); default void forEach(Consumer<? super T> action) { } }
- 22. Iterable.forEach public interface Iterable<T> { Iterator<T> iterator(); default void forEach(Consumer<? super T> action) { Objects.requireNonNull(action); for (T t : this) { action.accept(t); } } }
- 23. Before Java 8... Interfaces contain only method declarations and no implementations
- 24. With Java 8... Interfaces contain only method declarations and no implementations
- 26. Default methods Also called: Defender methods Virtual extension methods
- 27. Default methods Helped extending/improving the existing API interfaces... … without breaking the existing code... … by providing default implementations
- 28. Default methods Could be abused, for multiple inheritance!
- 29. Default methods Could be abused, for multiple inheritance! Multiple inheritance of type - been there, done that!
- 30. Default methods Could be abused, for multiple inheritance! Multiple inheritance of type - been there, done that! of behaviour - you are here!
- 31. Default methods Could be abused, for multiple inheritance! Multiple inheritance of type - been there, done that! of behaviour - you are here! of state - not yet, hopefully NOT EVER!
- 32. Default methods interface Foo { default void doIt() { /* foo impl */ } } interface Bar { default void doIt() { /* bar impl */ } } class FooBar implements Foo, Bar {} Will not compile
- 33. Default methods interface Foo { default void doIt() { /* foo impl */ } } interface Bar { default void doIt() { /* bar impl */ } } class FooBar implements Foo, Bar { @Override public void doIt() { Foo.super.doIt(); } }
- 35. Streams API Nothing to do with I/O Streams
- 36. Streams API Nothing to do with I/O Streams A pipes-and-filters based API for collections
- 37. Streams API Nothing to do with I/O Streams A pipes-and-filters based API for collections This may be familiar... ps -ef | grep java | cut -c 1-9 | sort -n | uniq
- 38. Streams API Nothing to do with I/O Streams A pipes-and-filters based API for collections This may be familiar... ps -ef | grep java | cut -c 1-9 | sort -n | uniq In a similar manner... blocks.stream() .filter(b -> b.getColor() == Color.RED) .mapToInt(b -> b.getWeight()).sum();
- 39. Method references documents .map(d -> d.getTitle()) .collect(toList());
- 40. Method references documents .map(d -> d.getTitle()) .collect(toList()); Does nothing but call an existing method...
- 41. Method references documents .map(d -> d.getTitle()) .collect(toList()); documents .map(Document::getTitle) .collect(toList());
- 42. Method references to a static method ContainingClass::staticMethodName
- 43. Method references to a static method ContainingClass::staticMethodName to an instance method of a particular object containingObject::instanceMethodName
- 44. Method references to a static method ContainingClass::staticMethodName to an instance method of a particular object containingObject::instanceMethodName to a constructor ClassName::new
- 45. See also... ● JSR 310: Date and Time API No more java.util.Calendar!!! ● Nashorn, the new Javascript engine var HelloUser = Java.type("com.credera.example.HelloUser"); var helloUser = new HelloUser("John"); print(helloUser.getMessage()) $ jjs -cp /com/credera/example/HelloUser TestNashorn.js
- 47. Play with it https://github.com/AdoptOpenJDK/lambda-tutorial https://jdk8.java.net/lambda/ IDE support: http://www.jetbrains.com/idea/download/ http://wiki.eclipse.org/JDT/Eclipse_Java_8_Support_(BETA) http://bits.netbeans.org/dev/nightly/latest/