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[BAEL-9555] - Created a core-java-modules folder

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This commit is contained in:
amit2103
2019-05-05 17:22:09 +05:30
parent 8b63b0d90a
commit 3bae5e5334
1480 changed files with 25600 additions and 5594 deletions
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13
core-java-modules/core-java-9/src/main/java/.gitignore vendored Normal file
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*.class
#folders#
/target
/neoDb*
/data
/src/main/webapp/WEB-INF/classes
*/META-INF/*
# Packaged files #
*.jar
*.war
*.ear

12
core-java-modules/core-java-9/src/main/java/com/baeldung/java9/aot/JaotCompilation.java Normal file
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package com.baeldung.java9.aot;
public class JaotCompilation {
public static void main(String[] argv) {
System.out.println(message());
}
public static String message() {
return "The JAOT compiler says 'Hello'";
}
}

23
core-java-modules/core-java-9/src/main/java/com/baeldung/java9/language/PrivateInterface.java Normal file
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package com.baeldung.java9.language;
public interface PrivateInterface {
private static String staticPrivate() {
return "static private";
}
private String instancePrivate() {
return "instance private";
}
public default void check() {
String result = staticPrivate();
if (!result.equals("static private"))
throw new AssertionError("Incorrect result for static private interface method");
PrivateInterface pvt = new PrivateInterface() {
};
result = pvt.instancePrivate();
if (!result.equals("instance private"))
throw new AssertionError("Incorrect result for instance private interface method");
}
}

27
core-java-modules/core-java-9/src/main/java/com/baeldung/java9/language/stream/StreamsGroupingCollectionFilter.java Normal file
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package com.baeldung.java9.language.stream;
import static java.util.stream.Collectors.filtering;
import static java.util.stream.Collectors.groupingBy;
import static java.util.stream.Collectors.toList;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.function.Function;
public class StreamsGroupingCollectionFilter {
static public Map<Integer, List<Integer>> findEvenNumbersAfterGroupingByQuantityOfDigits(Collection<Integer> baseCollection) {
Function<Integer, Integer> getQuantityOfDigits = item -> (int) Math.log10(item) + 1;
return baseCollection.stream()
.collect(groupingBy(getQuantityOfDigits, filtering(item -> item % 2 == 0, toList())));
}
static public Map<Integer, List<Integer>> findEvenNumbersBeforeGroupingByQuantityOfDigits(Collection<Integer> baseCollection) {
return baseCollection.stream()
.filter(item -> item % 2 == 0)
.collect(groupingBy(item -> (int) Math.log10(item) + 1, toList()));
}
}

33
core-java-modules/core-java-9/src/main/java/com/baeldung/java9/maps/initialize/MapsInitializer.java Normal file
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package com.baeldung.java9.maps.initialize;
import java.util.AbstractMap;
import java.util.HashMap;
import java.util.Map;
public class MapsInitializer {
@SuppressWarnings("unused")
public void createMapWithMapOf() {
Map<String, String> emptyMap = Map.of();
Map<String, String> singletonMap = Map.of("key1", "value");
Map<String, String> map = Map.of("key1","value1", "key2", "value2");
}
public void createMapWithMapEntries() {
Map<String, String> map = Map.ofEntries(
new AbstractMap.SimpleEntry<String, String>("name", "John"),
new AbstractMap.SimpleEntry<String, String>("city", "budapest"),
new AbstractMap.SimpleEntry<String, String>("zip", "000000"),
new AbstractMap.SimpleEntry<String, String>("home", "1231231231")
);
}
@SuppressWarnings("unused")
public void createMutableMaps() {
Map<String, String> map = new HashMap<String, String> (Map.of("key1","value1", "key2", "value2"));
Map<String, String> map2 = new HashMap<String, String> ( Map.ofEntries(
new AbstractMap.SimpleEntry<String, String>("name", "John"),
new AbstractMap.SimpleEntry<String, String>("city", "budapest")));
}
}

17
core-java-modules/core-java-9/src/main/java/com/baeldung/java9/methodhandles/Book.java Normal file
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package com.baeldung.java9.methodhandles;
public class Book {
String id;
String title;
public Book(String id, String title) {
this.id = id;
this.title = title;
}
@SuppressWarnings("unused")
private String formatBook() {
return id + " > " + title;
}
}

24
core-java-modules/core-java-9/src/main/java/com/baeldung/java9/rangedates/DatesCollectionIteration.java Normal file
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package com.baeldung.java9.rangedates;
import java.util.Collection;
import java.util.Date;
public class DatesCollectionIteration {
public void iteratingRangeOfDatesJava7(Collection<Date> dates) {
for (Date date : dates) {
processDate(date);
}
}
public void iteratingRangeOfDatesJava8(Collection<Date> dates) {
dates.stream()
.forEach(this::processDate);
}
private void processDate(Date date) {
System.out.println(date);
}
}

43
core-java-modules/core-java-9/src/main/java/com/baeldung/java9/rangedates/RangeDatesIteration.java Normal file
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package com.baeldung.java9.rangedates;
import java.time.LocalDate;
import java.util.Calendar;
import java.util.Date;
public class RangeDatesIteration {
public void iterateBetweenDatesJava9(LocalDate startDate, LocalDate endDate) {
startDate.datesUntil(endDate)
.forEach(this::processDate);
}
public void iterateBetweenDatesJava8(LocalDate start, LocalDate end) {
for (LocalDate date = start; date.isBefore(end); date = date.plusDays(1)) {
processDate(date);
}
}
public void iterateBetweenDatesJava7(Date start, Date end) {
Date current = start;
while (current.before(end)) {
processDate(current);
Calendar calendar = Calendar.getInstance();
calendar.setTime(current);
calendar.add(Calendar.DATE, 1);
current = calendar.getTime();
}
}
private void processDate(LocalDate date) {
System.out.println(date);
}
private void processDate(Date date) {
System.out.println(date);
}
}

82
core-java-modules/core-java-9/src/main/java/com/baeldung/java9/reactive/BaeldungBatchSubscriberImpl.java Normal file
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package com.baeldung.java9.reactive;
import java.util.ArrayList;
import java.util.concurrent.Flow.Subscriber;
import java.util.concurrent.Flow.Subscription;
public class BaeldungBatchSubscriberImpl<T> implements Subscriber<String> {
private Subscription subscription;
private boolean completed = false;
private int counter;
private ArrayList<String> buffer;
public static final int BUFFER_SIZE = 5;
public BaeldungBatchSubscriberImpl() {
buffer = new ArrayList<String>();
}
public boolean isCompleted() {
return completed;
}
public void setCompleted(boolean completed) {
this.completed = completed;
}
public int getCounter() {
return counter;
}
public void setCounter(int counter) {
this.counter = counter;
}
@Override
public void onSubscribe(Subscription subscription) {
this.subscription = subscription;
subscription.request(BUFFER_SIZE);
}
@Override
public void onNext(String item) {
buffer.add(item);
// if buffer is full, process the items.
if (buffer.size() >= BUFFER_SIZE) {
processBuffer();
}
//request more items.
subscription.request(1);
}
private void processBuffer() {
if (buffer.isEmpty())
return;
// Process all items in the buffer. Here, we just print it and sleep for 1 second.
System.out.print("Processed items: ");
buffer.stream()
.forEach(item -> {
System.out.print(" " + item);
});
System.out.println();
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
counter = counter + buffer.size();
buffer.clear();
}
@Override
public void onError(Throwable t) {
t.printStackTrace();
}
@Override
public void onComplete() {
completed = true;
// process any remaining items in buffer before
processBuffer();
subscription.cancel();
}
}

55
core-java-modules/core-java-9/src/main/java/com/baeldung/java9/reactive/BaeldungSubscriberImpl.java Normal file
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package com.baeldung.java9.reactive;
import java.util.concurrent.Flow.Subscriber;
import java.util.concurrent.Flow.Subscription;
public class BaeldungSubscriberImpl<T> implements Subscriber<String> {
private Subscription subscription;
private boolean completed = false;
private int counter;
public boolean isCompleted() {
return completed;
}
public void setCompleted(boolean completed) {
this.completed = completed;
}
public int getCounter() {
return counter;
}
public void setCounter(int counter) {
this.counter = counter;
}
@Override
public void onSubscribe(Subscription subscription) {
this.subscription = subscription;
subscription.request(1);
}
@Override
public void onNext(String item) {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
counter++;
System.out.println("Processed item : " + item);
subscription.request(1);
}
@Override
public void onError(Throwable t) {
t.printStackTrace();
}
@Override
public void onComplete() {
completed = true;
subscription.cancel();
}
}

44
core-java-modules/core-java-9/src/main/java/com/baeldung/java9/set/UnmodifiableSet.java Normal file
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package com.baeldung.java9.set;
import com.google.common.collect.ImmutableSet;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;
public class UnmodifiableSet {
public static void main(String[] args) {
Set<String> set = new HashSet<>();
set.add("Canada");
set.add("USA");
coreJDK(set);
guavaOf();
copyOf(set);
java9Of();
}
private static void java9Of() {
Set<String> immutable = Set.of("Canada", "USA");
System.out.println(immutable);
}
private static void guavaOf() {
Set<String> immutable = ImmutableSet.of("Canada", "USA");
System.out.println(immutable);
}
private static void copyOf(Set<String> set) {
Set<String> immutable = ImmutableSet.copyOf(set);
set.add("Costa Rica");
System.out.println(immutable);
}
private static void coreJDK(Set<String> set) {
Set<String> unmodifiableSet = Collections.unmodifiableSet(set);
set.add("Costa Rica");
System.out.println(unmodifiableSet);
}
}

84
core-java-modules/core-java-9/src/main/java/com/baeldung/java9/stackwalker/StackWalkerDemo.java Normal file
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package com.baeldung.java9.stackwalker;
import java.lang.StackWalker.StackFrame;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;
public class StackWalkerDemo {
public void methodOne() {
this.methodTwo();
}
public void methodTwo() {
this.methodThree();
}
public void methodThree() {
List<StackFrame> stackTrace = StackWalker.getInstance()
.walk(this::walkExample);
printStackTrace(stackTrace);
System.out.println("---------------------------------------------");
stackTrace = StackWalker.getInstance()
.walk(this::walkExample2);
printStackTrace(stackTrace);
System.out.println("---------------------------------------------");
String line = StackWalker.getInstance().walk(this::walkExample3);
System.out.println(line);
System.out.println("---------------------------------------------");
stackTrace = StackWalker.getInstance(StackWalker.Option.SHOW_REFLECT_FRAMES)
.walk(this::walkExample);
printStackTrace(stackTrace);
System.out.println("---------------------------------------------");
Runnable r = () -> {
List<StackFrame> stackTrace2 = StackWalker.getInstance(StackWalker.Option.SHOW_HIDDEN_FRAMES)
.walk(this::walkExample);
printStackTrace(stackTrace2);
};
r.run();
}
public List<StackFrame> walkExample(Stream<StackFrame> stackFrameStream) {
return stackFrameStream.collect(Collectors.toList());
}
public List<StackFrame> walkExample2(Stream<StackFrame> stackFrameStream) {
return stackFrameStream.filter(frame -> frame.getClassName()
.contains("com.baeldung"))
.collect(Collectors.toList());
}
public String walkExample3(Stream<StackFrame> stackFrameStream) {
return stackFrameStream.filter(frame -> frame.getClassName()
.contains("com.baeldung")
&& frame.getClassName()
.endsWith("Test"))
.findFirst()
.map(frame -> frame.getClassName() + "#" + frame.getMethodName() + ", Line " + frame.getLineNumber())
.orElse("Unknown caller");
}
public void findCaller() {
Class<?> caller = StackWalker.getInstance(StackWalker.Option.RETAIN_CLASS_REFERENCE).getCallerClass();
System.out.println(caller.getCanonicalName());
}
public void printStackTrace(List<StackFrame> stackTrace) {
for (StackFrame stackFrame : stackTrace) {
System.out.println(stackFrame.getClassName()
.toString() + "#" + stackFrame.getMethodName() + ", Line " + stackFrame.getLineNumber());
}
}
}

43
core-java-modules/core-java-9/src/main/java/com/baeldung/java9/streams.reactive/EndSubscriber.java Normal file
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package com.baeldung.java9.streams.reactive;
import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.Flow.Subscriber;
import java.util.concurrent.Flow.Subscription;
import java.util.concurrent.atomic.AtomicInteger;
public class EndSubscriber<T> implements Subscriber<T> {
private final AtomicInteger howMuchMessagesToConsume;
private Subscription subscription;
public List<T> consumedElements = new LinkedList<>();
public EndSubscriber(Integer howMuchMessagesToConsume) {
this.howMuchMessagesToConsume = new AtomicInteger(howMuchMessagesToConsume);
}
@Override
public void onSubscribe(Subscription subscription) {
this.subscription = subscription;
subscription.request(1);
}
@Override
public void onNext(T item) {
howMuchMessagesToConsume.decrementAndGet();
System.out.println("Got : " + item);
consumedElements.add(item);
if (howMuchMessagesToConsume.get() > 0) {
subscription.request(1);
}
}
@Override
public void onError(Throwable t) {
t.printStackTrace();
}
@Override
public void onComplete() {
System.out.println("Done");
}
}

38
core-java-modules/core-java-9/src/main/java/com/baeldung/java9/streams.reactive/TransformProcessor.java Normal file
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package com.baeldung.java9.streams.reactive;
import java.util.concurrent.Flow;
import java.util.concurrent.SubmissionPublisher;
import java.util.function.Function;
public class TransformProcessor<T, R> extends SubmissionPublisher<R> implements Flow.Processor<T, R> {
private Function<T, R> function;
private Flow.Subscription subscription;
public TransformProcessor(Function<T, R> function) {
super();
this.function = function;
}
@Override
public void onSubscribe(Flow.Subscription subscription) {
this.subscription = subscription;
subscription.request(1);
}
@Override
public void onNext(T item) {
submit(function.apply(item));
subscription.request(1);
}
@Override
public void onError(Throwable t) {
t.printStackTrace();
}
@Override
public void onComplete() {
close();
}
}

16
core-java-modules/core-java-9/src/main/java/com/baeldung/multireleaseapp/App.java Normal file
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package com.baeldung.multireleaseapp;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class App {
private static final Logger logger = LoggerFactory.getLogger(App.class);
public static void main(String[] args) throws Exception {
String dateToCheck = args[0];
boolean isLeapYear = DateHelper.checkIfLeapYear(dateToCheck);
logger.info("Date given " + dateToCheck + " is leap year: " + isLeapYear);
}
}

22
core-java-modules/core-java-9/src/main/java/com/baeldung/multireleaseapp/DateHelper.java Normal file
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package com.baeldung.multireleaseapp;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.GregorianCalendar;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class DateHelper {
private static final Logger logger = LoggerFactory.getLogger(DateHelper.class);
public static boolean checkIfLeapYear(String dateStr) throws Exception {
logger.info("Checking for leap year using Java 1 calendar API");
Calendar cal = Calendar.getInstance();
cal.setTime(new SimpleDateFormat("yyyy-MM-dd").parse(dateStr));
int year = cal.get(Calendar.YEAR);
return (new GregorianCalendar()).isLeapYear(year);
}
}

26
core-java-modules/core-java-9/src/main/java/com/baeldung/optionals/Optionals.java Normal file
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package com.baeldung.optionals;
import java.util.Optional;
public class Optionals {
public static <T> Optional<T> or(Optional<T> optional, Optional<T> fallback) {
return optional.isPresent() ? optional : fallback;
}
public static Optional<String> getName(Optional<String> name) {
return name.or(() -> getCustomMessage());
}
public static com.google.common.base.Optional<String> getOptionalGuavaName(com.google.common.base.Optional<String> name) {
return name.or(getCustomMessageGuava());
}
private static Optional<String> getCustomMessage() {
return Optional.of("Name not provided");
}
private static com.google.common.base.Optional<String> getCustomMessageGuava() {
return com.google.common.base.Optional.of("Name not provided");
}
}

18
core-java-modules/core-java-9/src/main/java9/com/baeldung/multireleaseapp/DateHelper.java Normal file
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package com.baeldung.multireleaseapp;
import java.time.LocalDate;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class DateHelper {
private static final Logger logger = LoggerFactory.getLogger(DateHelper.class);
public static boolean checkIfLeapYear(String dateStr) throws Exception {
logger.info("Checking for leap year using Java 9 Date Api");
return LocalDate.parse(dateStr)
.isLeapYear();
}
}

19
core-java-modules/core-java-9/src/main/resources/logback.xml Normal file
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<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
<encoder>
<pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n
</pattern>
</encoder>
</appender>
<logger name="org.springframework" level="WARN" />
<logger name="org.springframework.transaction" level="WARN" />
<!-- in order to debug some marshalling issues, this needs to be TRACE -->
<logger name="org.springframework.web.servlet.mvc" level="WARN" />
<root level="INFO">
<appender-ref ref="STDOUT" />
</root>
</configuration>