Merge branch 'master' into BAEL-16633

core-java-modules/core-java-9/src/main/java/com/baeldung/java9/language/stream/StreamsGroupingCollectionFilter.java

@@ -0,0 +1,27 @@
+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()));
+    }
+}

core-java-modules/core-java-9/src/main/java/com/baeldung/java9/maps/initialize/MapsInitializer.java

@@ -0,0 +1,33 @@
+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")));
+        
+    }
+}

core-java-modules/core-java-9/src/main/java/com/baeldung/java9/methodhandles/Book.java

@@ -0,0 +1,17 @@
+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;
+    }
+}

core-java-modules/core-java-9/src/main/java/com/baeldung/java9/rangedates/DatesCollectionIteration.java

@@ -0,0 +1,24 @@
+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);
+    }
+
+}

core-java-modules/core-java-9/src/main/java/com/baeldung/java9/rangedates/RangeDatesIteration.java

@@ -0,0 +1,43 @@
+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);
+    }
+}

core-java-modules/core-java-9/src/main/java/com/baeldung/java9/set/UnmodifiableSet.java

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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);
+    }
+}

core-java-modules/core-java-9/src/main/java/com/baeldung/optionals/Optionals.java

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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");
+    }
+} 

core-java-modules/core-java-9/src/main/resources/logback.xml

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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>