Java 8 고급 (6/6)
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The document outlines a six-day training plan on Java, covering topics from basic language features to advanced concepts such as lambda expressions and functional programming. It includes detailed discussions on Java 8's contributions, such as default methods in interfaces, the use of streams, and the implications of invoking methods with method handles. Additionally, it emphasizes the performance comparisons between different invocation methods and the importance of closures in functional programming.
![Method Reference expression
method reference : refer to a method without invoking it
System::getProperty
"abc"::length
constructor reference : refer to a constructor without creating
a new instance of the named class or array type
ArrayList::new
int[]::new
e.g, Arrays.sort(myIntegerArray, Integer::compare)
10
1013년 10월 22일 화](https://image.slidesharecdn.com/java6-200601074430/85/Java-8-6-6-10-320.jpg)
![Lambda Invocation
desugar implementation method
private static boolean lambda$1(int minAge, Person p) { ... }
lambda metafactory에 MethodHandle argument로 전달
invokeDynamic 호출
Predicate $p = invokedynamic[bootstrap=LambdaMetaFactory, ... ]
moving more work from static compiler to runtime
performance
linkage, capture 비용은 inner class보다 싸지만 invoke 비용은 비싸다!
23
2313년 10월 22일 화](https://image.slidesharecdn.com/java6-200601074430/85/Java-8-6-6-23-320.jpg)
Java 8 고급 (6/6)
- 1. Java 엿새째 TmaxSoft R&D Center 1 113년 10월 22일 화
- 2. 자바 교육 계획 1일 : Language, String, ClassLoader, Proxy 2일 : GC, Collections 3일 : Thread, Java Memory Model 4일 : AQS, ForkJoin, Concurrent Utils 5일 : IO, Generics, Annotation, RMI 6일 : Unsafe, Lambda (Java 8) 2 내겐 바스켓만 보여 (Flow 상태) 213년 10월 22일 화
- 3. 오늘 내용 sun.misc.Unsafe Lambda (Java 8) 3 313년 10월 22일 화
- 5. sun.misc.Unsafe 5 A collection of methods for performing low-level, unsafe operations park, unpark direct memory manipulation provide wrappers for malloc, realloc, free, memset, memcpy (not Java Heap) direct object memory manipulation CAS operations : compareAndSwap defineClass, defineAnonymousClass 513년 10월 22일 화
- 6. Java is not safe with Unsafe 6 can easily corrupt memory fast serialization super array (non-Java heap) allocateMemory(long size) can cause JVM crash 613년 10월 22일 화
- 7. Lambda 7 The issue being debated is not whether closures are a good idea -‐ because they clearly are -‐ but whether the benefits of retrofi7ng the Java language with closures are worth the costs. -‐ Brian Goetz 713년 10월 22일 화
- 8. Functional Programming 8 lambda anonymous function with a single argument closure a block of code that may contain free (unbound) variables currying handling multiple argument function with lambda function 813년 10월 22일 화
- 9. Java 8 Lambda Expression SAM (single abstract method) of an interface Java lambda expression a list of formal parameters and a body—an expression or block—expressed in terms of those parameters e.g, s -> s.toUpperCase() (int a, int b) -> a + b 9 913년 10월 22일 화
- 10. Method Reference expression method reference : refer to a method without invoking it System::getProperty "abc"::length constructor reference : refer to a constructor without creating a new instance of the named class or array type ArrayList::new int[]::new e.g, Arrays.sort(myIntegerArray, Integer::compare) 10 1013년 10월 22일 화
- 11. Java 8 Closure For both lambda bodies and inner classes, local variables in the enclosing context can only be referenced if they are final or effectively final. A variable is effectively final if it is never assigned to after its initialization. 11 1113년 10월 22일 화
- 12. Java 8 Currying Currying :A technique of transforming a multi-argument function in such a way that it can be called as a chain of functions, each with a single argument. 12 1213년 10월 22일 화
- 13. New Object-oriented feature mixin a class which contains a combination of methods from other classes. can also be viewed as an interface with implemented methods. Mixins encourage code reuse and avoid well-known pathologies associated with multiple inheritance. 13 1313년 10월 22일 화
- 14. Java 8 Default Method Java’s language addition of mixin-like thing provides a default implementation for any class that implements the interface without overriding the method. allows new functionality to be added to existing (and perhaps already widely-distributed) interfaces. More generally, it provides a mechanism for multiple inheritance of behavior. 14 1413년 10월 22일 화
- 15. Java 8 Changes to Interface Now, interface method can be default, static and abstract all the non-default, non-static methods in the interface are abstract as before Default methods of super-interface can be accessed <InterfaceName>.super.<methodName>() 15 1513년 10월 22일 화
- 16. Java 8 Project Lambda Language Changes Still, No Function Type Functional Interface Default Method Streams invokeDynamic java.util.Spliterator 16 1613년 10월 22일 화
- 17. Java Lambda ABC @interface java.lang.FunctionalInterface Just a hint for compiler (compile error if does not have SAM) any interface which has SAM is functional interface package java.util.function lambda function does not create additional classes unlike anonymous inner classes it creates a private static lambda method 17 1713년 10월 22일 화
- 18. Streams handle aggregate operations DECLARATIVELY stream pipeline 1 source : collection, array, generator ftn, IO, ... 0 or more intermediate operations : filter, map, ... 1 terminal operation : forEach, reduce, sum, ... 18 1813년 10월 22일 화
- 19. Stages of Streams txns.stream() .filter(txn -> txn.getBuyer().getAge() >= 65) .map(txn -> txn.getSeller()) .distinct() .sort(comparing(seller -> seller.getName())) .forEach(seller -> System.out.println(seller.getName()); 19 source intermediate intermediate intermediate intermediate terminal intermediate ops just setup pipeline and returns new stream 1913년 10월 22일 화
- 20. Parallel Streams A stream pipeline can be created with an orientation of either serial or parallel Parallelism may be faster but introduces non-determinism Internally uses fork-join framework Collection c = ...; List r1 = c.stream().map(...).collect(toList()); List r2 = c.parallelStream().map(...).collect(toList()); 20 2013년 10월 22일 화
- 21. Parallel Streams 21 2113년 10월 22일 화
- 22. MethodHandle java.lang.invoke 패키지 can store references to methods in the constant pool, load with LDC (load constant) can obtain a method handle for any method (or field access) But MethodHandle invocation performance is not good Lambda is language level method, MethodHandle is VM level method 22 2213년 10월 22일 화
- 23. Lambda Invocation desugar implementation method private static boolean lambda$1(int minAge, Person p) { ... } lambda metafactory에 MethodHandle argument로 전달 invokeDynamic 호출 Predicate $p = invokedynamic[bootstrap=LambdaMetaFactory, ... ] moving more work from static compiler to runtime performance linkage, capture 비용은 inner class보다 싸지만 invoke 비용은 비싸다! 23 2313년 10월 22일 화
- 24. invokeDynamic invokeStatic System.currentTimeMillis(), Math.log(1.0) invokeVirtual "hello".toUpperCase(), System.out.println() invokeInterface myList.add("happy happy"), myRunnable.run() invokeSpecial (constructor or super call) new ArrayList(), super.equals(other) 성능 비교 invokeStatic (2.7배) >> invokeDynamic (12.6배) >> reflection 24 2413년 10월 22일 화
- 25. 다음 시간 예정 JEUS Web Engine 25 여러분의 전성시대는 언제였나요? 2513년 10월 22일 화