모던자바의 역습

김대우
젬플레이 이사
http://lekdw.blogspot.kr/
정도현(정개발)
나는 프로그래머다 MC
일본 Mamezou소속 컨설턴트
http://Iamprogrammer.io
http://moreagile.net

James Gosling
Patrick Naughton
https://en.wikipedia.org/wiki/Java_(programming_language)

https://en.wikipedia.org/wiki/Java_(programming_language)

J2SE 5.0
Java SE 7
Java SE 8
https://en.wikipedia.org/wiki/Java_version_history

연도별 언어 인기도
http://www.tiobe.com/index.p
hp/content/paperinfo/tpci/ind
ex.html

http://benchmarksgame.alioth.debian.org/u64/which-programs-are-fastest.html

http://www3.ntu.edu.sg/home/ehchua/programming/java/j5b_io.html

http://www.evanjones.ca/software/java-bytebuffers.html

http://netty.io/wiki/using-as-a-generic-library.html

http://terracotta.org/products/bigmemory

모바일 게임 서버와 같이 Life Cycle이 짧은 데이터(객체)를 주로 처리하
는 경우, 별다른 튜닝없이 -server, -d64, -Xms, -Xmx 옵션으로 충분.

http://www.drdobbs.com/jvm/the-comparative-productivity-of-programm/240005881
Language Hours Per Function Point
ASP* 06.1
Visual Basic 08.5
Java 10.6
SQL 10.8
C++ 12.4
C 13.0
C# 15.5
PL/1 14.2
COBOL 16.8
ABAP 19.9

Checkstyle
Error Prone
FindBugs
PMD
SonarQube

http://readwrite.com/2011/01/24/the-java-ecosystem-infographic

JUnit
SLF4J API Module
Scala Library
Logback Classic Module
Guava: Google Core Libraries for Java
Mockito
Google APIs Client Library for Java
Apache Log4j
Commons IO
SLF4J LOG4J-12 Binding
osgi.core
JavaServlet(TM) Specification
TestNG
ScalaTest
Commons Lang
Joda-Time
Spring Context
Mockito
H2 Database Engine
Java Servlet API
http://www.77dev.com/2014/05/java-trends-top-100-mostly-used.html

JCL 1.1.1 implemented over SLF4J
jackson-databind
SLF4J Simple Binding
Apache CommonsCodec
Apache HttpClient
Apache Commons Lang
Commons Logging
Spring Core
osgi.cmpn
Google Guice - Core Library
SpringTestContext Framework
Jetty :: Server Core
Maven Plugin API
FindBugs-jsr305
BeanValidation API
Spring Beans
Groovy
Jackson-core
EasyMock
Spock Framework - Core Module

http://www.slideshare.net/shintanimoto/from-old-java-to-modern-java

private List m_list=null;
private int process_file(String str_file_name){
String str_line;
List list_lines=new ArrayList();
int i_result=read_file(str_file_name,list_lines);
if(i_result==0){
List list_record=new ArrayList();
for(int i=0;i<list_lines.size();i++){
str_line=(String)list_lines.get(i);
Record record=new Record();
i_result=parse_line(str_line,record);
if(i_result!=0){
return i_result;
}
list_recordord.add(record);
}
m_list=list_record;
return 0;
}else{
return i_result;
}
}
C-ish java

private List resultList;
private List processFile(String ﬁleName)throws
SystemException {
List lines = readFile(ﬁleName);
List recordList = new ArrayList();
for (int i = 0; i < lines.size(); i++) {
String line = (String) lines.get(i);
Record record = parseLine(line);
recordList.add(record);
}
return recordList;
}
Java 1.4

private List<Record> processFile(String ﬁleName)throws SystemException {
List<String> lines = readFile(ﬁleName);
List<Record> recordList = new ArrayList();
for (String line : lines) {
Record record = parseLine(line);
recordList.add(record);
}
return recordList;
}
Java 1.7 generic + foreach

private List<String> readFile(String fileName) {
List<String> lines = new ArrayList<String>();
BufferedReader reader = null;
try {
reader = new BufferedReader(new FileReader(fileName));
String line;
while ((line = reader.readLine()) != null) {
lines.add(line);
}
} catch (FileNotFoundException ex) {
throw new SystemException(FILE_NOT_FOUND, ex);
} catch (IOException ex) {
throw new SystemException(FILE_READ_ERROR, ex);
}
finally {
try {
if (reader != null) {
reader.close();
}
// 이건 무시?
}
}
return lines;
}

List<String> lines = new ArrayList<>();
try (FileReader in = new FileReader(ﬁleName);
BufferedReader reader = new BufferedReader(in)) {
String line;
while ((line = reader.readLine()) != null) {
lines.add(line);
}
} catch (FileNotFoundException ex) {
throw new SystemException(FILE_NOT_FOUND, ex);
}
return lines;
}
Java 7

try {
return Files.readAllLines(Paths.get(ﬁleName), Charset.defaultCharset());
}
}
Java 7

https://ko.wikipedia.org/wiki/함수형_프로그래
밍

public static <E extends Comparable<? super E>>
List<E> quickSort(List<E> arr) {
if (!arr.isEmpty()) {
E pivot = arr.get(0); //This pivot can change
to get faster results
List<E> less = new LinkedList<E>();
List<E> pivotList = new LinkedList<E>();
List<E> more = new LinkedList<E>();
for (E i: arr) {
if (i.compareTo(pivot) < 0)
less.add(i);
else if (i.compareTo(pivot) > 0)
more.add(i);
else
pivotList.add(i);
}
less = quickSort(less);
more = quickSort(more);
less.addAll(pivotList);
less.addAll(more);
return less;
}
return arr;
}
http://rosettacode.org/wiki/Sorting_algorithms/Quicksort#Java
Java 7

public static <T> List<T> Quicksort(List<T> v, BiFunction<T, T,
Integer> comparer) {
if (v.size() < 2)
return v;
T pivot = v.get(v.size() / 2);
List<T> l = new LinkedList<T>(Quicksort(v.stream()
.filter(x -> comparer.apply(x, pivot) < 0)
.collect(Collectors.toList()), comparer));
l.addAll( v.stream().filter(x -> comparer
.apply(x, pivot) == 0).collect(Collectors.toList()) );
l.addAll( Quicksort(v.stream()
.filter(x -> comparer.apply(x, pivot) > 0)
.collect(Collectors.toList()), comparer) );
return l;
}
Java 8

qsort [] = []
qsort (x:xs) = qsort (filter (< x) xs) ++ [x] ++ qsort (filter (>= x) xs)
https://en.wikibooks.org/wiki/Algorithm_Implementation/Sorting/Quicksort#Haskell
Haskell

package org.ingini.spark.java8;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.Arrays;
import java.util.TreeMap;
import static java.util.function.Function.identity;
import static java.util.stream.Collectors.counting;
import static java.util.stream.Collectors.groupingBy;
public class WordsCounterJava {
public static final String REGEX = "s+";
public TreeMap<String, Long> count(String source) throws IOException {
return Files.lines(Paths.get(source))
.map(line -> line.split(REGEX))
.flatMap(Arrays::stream)
.collect(groupingBy(identity(), TreeMap::new, counting()));
}
}

-Djava.util.concurrent.ForkJoinPool.common.parallelism=1

SELECT * FROM BOOK
WHERE BOOK.PUBLISHED_IN = 2011
ORDER BY BOOK.TITLE
jOOQ
create.selectFrom(BOOK)
.where(BOOK.PUBLISHED_IN.eq(2011))
.orderBy(BOOK.TITLE)
http://www.jooq.org/

http://java2practice.com/2014/03/16/java-8-functional-interface-example/
Thread t =new Thread(new Runnable(){
public void run(){
System.out.println("Runnable implemented by using Lambda Expression");
}
});
Thread t = new Thread(()->{
System.out.println("Runnable implemented by using Lambda Expression");
});
Java 7
Java 8

interface DefaultInterfaceTest{
void show();
default void display(){
System.out.println("Default method from interface can have body..!");
}
}
public class DefaultInterfaceTestImpl implements DefaultInterfaceTest{
public void show(){
System.out.println("show method");
}
//we dont need to provide any implementation to default method.
public static void main(String[] args){
DefaultInterfaceTest obj = new DefaultInterfaceTestImpl();
obj.show();//out puts: show method
obj.display();//outputs : Default method from interface can have body..!
}
}
Default Method

•Function <T, R> - T를 입력으로 R을 출력으로 반환
•Predicate <T> - T를 입력으로 boolean을 출력으로 반환
•Consumer <T> - T를 입력으로 아무것도 반환하지 않는다
•Supplier <T> - 입력을 취하지 않고 T를 반환
•BinaryOperator <T> - 2 개의 T를 입력으로 하나의 T를 출력으로
반환

http://www.ibm.com/developerworks/library/j-jvmc2/index.html

Runnable task = () -> {
String threadName = Thread.currentThread().getName();
System.out.println("Hello " + threadName);
};
task.run();
Thread thread = new Thread(task);
thread.start();

ExecutorService executor = Executors.newSingleThreadExecutor();
executor.submit(() -> {
String threadName = Thread.currentThread().getName();
System.out.println("Hello " + threadName);
});
try {
//attempt to shutdown executor
executor.shutdown();
executor.awaitTermination(5, TimeUnit.SECONDS);
}
catch (InterruptedException e) {
System.err.println("tasks interrupted");
}
finally {
if (!executor.isTerminated()) {
executor.shutdownNow();
}
System.out.println("shutdown finished");
}
Executors
http://winterbe.com/posts/2015/04/07/java8-concurrency-tutorial-thread-executor-examples/

http://ariya.ofilabs.com/2014/03/nashorn-the-new-rhino-on-the-block.html

interface CustomerRepository extends Repository<Customer, Long> {
@Query("select c from Customer c")
Stream<Customer> streamAllCustomers();
}
try (Stream<Customer> customers = repository.streamAllCustomers()) {
// use the stream here
}
Support for JDK 8' Stream in repository methods

interface CustomerRepository extends Repository<Customer, Long> {
@Async
CompletableFuture<List<Customer>> readAllBy();
}
CompletableFuture<List<Customer>> future =
repository.readAllBy().thenApply(this::doSomethingWithCustomers);
while (!future.isDone()) {
log.info("Waiting for the CompletableFuture to finish...");
TimeUnit.MILLISECONDS.sleep(500);
}
List<Customer> processedCustomers = future.get();

http://doc.akka.io/docs/akka/2.3.0-RC1/java/lambda-actors.html
import akka.actor.AbstractActor;
import akka.event.Logging;
import akka.event.LoggingAdapter;
import akka.japi.pf.ReceiveBuilder;
import scala.PartialFunction;
import scala.runtime.BoxedUnit;
public class MyActor extends AbstractActor {
private final LoggingAdapter log = Logging.getLogger(context().system(), this);
@Override
public PartialFunction<Object, BoxedUnit> receive() {
return ReceiveBuilder.
match(String.class, s -> s.equals("test"), s -> log.info("received test")).
matchAny(o -> log.info("received unknown message")).build();
}
}

https://blogs.oracle.com/javatraining/entry/announcing_jdk_8_mooc_lambdas

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