Collapse core-java-8 into core-java

core-java/README.md

@@ -24,4 +24,19 @@
 - [Guide to Java 8’s Functional Interfaces](http://www.baeldung.com/java-8-functional-interfaces)
 - [Convert char to String in Java](http://www.baeldung.com/java-convert-char-to-string)
 - [Random List Element](http://www.baeldung.com/java-random-list-element)
-- [Convert String to int or Integer in Java](http://www.baeldung.com/java-convert-string-to-int-or-integer)
+- [Convert String to int or Integer in Java](http://www.baeldung.com/java-convert-string-to-int-or-integer)
+
+- [Java 8 – Powerful Comparison with Lambdas](http://www.baeldung.com/java-8-sort-lambda)
+- [Java – Directory Size](http://www.baeldung.com/java-folder-size)
+- [Java – Try with Resources](http://www.baeldung.com/java-try-with-resources)
+- [A Guide to the Java ExecutorService](http://www.baeldung.com/java-executor-service-tutorial)
+- [Java 8 New Features](http://www.baeldung.com/java-8-new-features)
+- [Lambda Expressions and Functional Interfaces: Tips and Best Practices](http://www.baeldung.com/java-8-lambda-expressions-tips)
+- [The Double Colon Operator in Java 8](http://www.baeldung.com/java-8-double-colon-operator)
+- [Java 8 Streams Advanced](http://www.baeldung.com/java-8-streams)
+- [Introduction to Thread Pools in Java](http://www.baeldung.com/thread-pool-java-and-guava)
+- [Guide to Java 8 Collectors](http://www.baeldung.com/java-8-collectors)
+- [The Java 8 Stream API Tutorial](http://www.baeldung.com/java-8-streams)
+- [New Features in Java 8](http://www.baeldung.com/java-8-new-features)
+- [Introduction to Java 8 Streams](http://www.baeldung.com/java-8-streams-introduction)
+- [Guide to the Fork/Join Framework in Java](http://www.baeldung.com/java-fork-join)

core-java/src/main/java/com/baeldung/.gitignore

@@ -0,0 +1,13 @@
+*.class
+
+#folders#
+/target
+/neoDb*
+/data
+/src/main/webapp/WEB-INF/classes
+*/META-INF/*
+
+# Packaged files #
+*.jar
+*.war
+*.ear

core-java/src/main/java/com/baeldung/Adder.java

@@ -0,0 +1,12 @@
+package com.baeldung;
+
+import java.util.function.Consumer;
+import java.util.function.Function;
+
+public interface Adder {
+
+    String addWithFunction(Function<String, String> f);
+
+    void addWithConsumer(Consumer<Integer> f);
+
+}

core-java/src/main/java/com/baeldung/AdderImpl.java

@@ -0,0 +1,17 @@
+package com.baeldung;
+
+import java.util.function.Consumer;
+import java.util.function.Function;
+
+public class AdderImpl implements Adder {
+
+    @Override
+    public String addWithFunction(final Function<String, String> f) {
+        return f.apply("Something ");
+    }
+
+    @Override
+    public void addWithConsumer(final Consumer<Integer> f) {
+    }
+
+}

core-java/src/main/java/com/baeldung/Bar.java

@@ -0,0 +1,12 @@
+package com.baeldung;
+
+@FunctionalInterface
+public interface Bar {
+
+    String method(String string);
+
+    default String defaultMethod() {
+        return "String from Bar";
+    }
+
+}

core-java/src/main/java/com/baeldung/Baz.java

@@ -0,0 +1,11 @@
+package com.baeldung;
+
+@FunctionalInterface
+public interface Baz {
+
+    String method(String string);
+
+    default String defaultMethod() {
+        return "String from Baz";
+    }
+}

core-java/src/main/java/com/baeldung/Foo.java

@@ -0,0 +1,10 @@
+package com.baeldung;
+
+@FunctionalInterface
+public interface Foo {
+
+    String method(String string);
+
+    default void defaultMethod() {
+    }
+}

core-java/src/main/java/com/baeldung/FooExtended.java

@@ -0,0 +1,11 @@
+package com.baeldung;
+
+@FunctionalInterface
+public interface FooExtended extends Baz, Bar {
+
+    @Override
+    default String defaultMethod() {
+        return Bar.super.defaultMethod();
+    }
+
+}

core-java/src/main/java/com/baeldung/UseFoo.java

@@ -0,0 +1,37 @@
+package com.baeldung;
+
+import java.util.function.Function;
+
+public class UseFoo {
+
+    private String value = "Enclosing scope value";
+
+    public String add(final String string, final Foo foo) {
+        return foo.method(string);
+    }
+
+    public String addWithStandardFI(final String string, final Function<String, String> fn) {
+        return fn.apply(string);
+    }
+
+    public String scopeExperiment() {
+        final Foo fooIC = new Foo() {
+            String value = "Inner class value";
+
+            @Override
+            public String method(final String string) {
+                return value;
+            }
+        };
+        final String resultIC = fooIC.method("");
+
+        final Foo fooLambda = parameter -> {
+            final String value = "Lambda value";
+            return this.value;
+        };
+        final String resultLambda = fooLambda.method("");
+
+        return "Results: resultIC = " + resultIC + ", resultLambda = " + resultLambda;
+    }
+
+}

core-java/src/main/java/com/baeldung/datetime/README.md

@@ -0,0 +1,2 @@
+### Relevant Articles:
+- [Introduction to the Java 8 Date/Time API](http://www.baeldung.com/java-8-date-time-intro)

core-java/src/main/java/com/baeldung/datetime/UseDuration.java

@@ -0,0 +1,16 @@
+package com.baeldung.datetime;
+
+import java.time.Duration;
+import java.time.LocalTime;
+import java.time.Period;
+
+public class UseDuration {
+    
+    public LocalTime modifyDates(LocalTime localTime,Duration duration){
+        return localTime.plus(duration);
+    }
+    
+    public Duration getDifferenceBetweenDates(LocalTime localTime1,LocalTime localTime2){
+        return Duration.between(localTime1, localTime2);
+    }
+}

core-java/src/main/java/com/baeldung/datetime/UseLocalDate.java

@@ -0,0 +1,46 @@
+package com.baeldung.datetime;
+
+import java.time.DayOfWeek;
+import java.time.LocalDate;
+import java.time.LocalDateTime;
+import java.time.temporal.ChronoUnit;
+import java.time.temporal.TemporalAdjusters;
+
+public class UseLocalDate {
+    
+    public LocalDate getLocalDateUsingFactoryOfMethod(int year, int month, int dayOfMonth){        
+        return LocalDate.of(year, month, dayOfMonth);
+    }
+    
+    public LocalDate getLocalDateUsingParseMethod(String representation){        
+        return LocalDate.parse(representation);
+    }
+    
+    public LocalDate getLocalDateFromClock(){        
+        LocalDate localDate = LocalDate.now();
+        return localDate;
+    }
+    
+    public LocalDate getNextDay(LocalDate localDate){       
+        return localDate.plusDays(1);
+    }
+    
+    public LocalDate getPreviousDay(LocalDate localDate){        
+        return localDate.minus(1, ChronoUnit.DAYS);
+    }
+    
+    public DayOfWeek getDayOfWeek(LocalDate localDate){        
+        DayOfWeek day = localDate.getDayOfWeek();
+        return day;
+    }
+    
+    public LocalDate getFirstDayOfMonth(){        
+        LocalDate firstDayOfMonth = LocalDate.now().with(TemporalAdjusters.firstDayOfMonth());
+        return firstDayOfMonth;
+    }
+    
+    public LocalDateTime getStartOfDay(LocalDate localDate){        
+        LocalDateTime startofDay = localDate.atStartOfDay();
+        return startofDay;
+    }
+}

core-java/src/main/java/com/baeldung/datetime/UseLocalDateTime.java

@@ -0,0 +1,11 @@
+package com.baeldung.datetime;
+
+import java.time.LocalDateTime;
+
+public class UseLocalDateTime {
+    
+    public LocalDateTime getLocalDateTimeUsingParseMethod(String representation){        
+        return LocalDateTime.parse(representation);
+    }
+
+}

core-java/src/main/java/com/baeldung/datetime/UseLocalTime.java

@@ -0,0 +1,35 @@
+package com.baeldung.datetime;
+
+import java.time.LocalTime;
+import java.time.temporal.ChronoUnit;
+
+public class UseLocalTime {
+    
+    public LocalTime getLocalTimeUsingFactoryOfMethod(int hour, int min, int seconds){        
+        LocalTime localTime = LocalTime.of(hour, min, seconds);
+        return localTime;
+    }
+    
+    public LocalTime getLocalTimeUsingParseMethod(String timeRepresentation){        
+        LocalTime localTime = LocalTime.parse(timeRepresentation);
+        return localTime;
+    }
+    
+    public LocalTime getLocalTimeFromClock(){        
+        LocalTime localTime = LocalTime.now();
+        return localTime;
+    }
+    
+    public LocalTime addAnHour(LocalTime localTime){
+        LocalTime newTime = localTime.plus(1,ChronoUnit.HOURS);
+        return newTime;
+    }
+    
+    public int getHourFromLocalTime(LocalTime localTime){        
+        return localTime.getHour();
+    }
+    
+    public LocalTime getLocalTimeWithMinuteSetToValue(LocalTime localTime, int minute){        
+        return localTime.withMinute(minute);
+    }
+}

core-java/src/main/java/com/baeldung/datetime/UsePeriod.java

@@ -0,0 +1,15 @@
+package com.baeldung.datetime;
+
+import java.time.LocalDate;
+import java.time.Period;
+
+public class UsePeriod {
+    
+    public LocalDate modifyDates(LocalDate localDate,Period period){
+        return localDate.plus(period);
+    }
+    
+    public Period getDifferenceBetweenDates(LocalDate localDate1,LocalDate localDate2){
+        return Period.between(localDate1, localDate2);
+    }
+}

core-java/src/main/java/com/baeldung/datetime/UseToInstant.java

@@ -0,0 +1,19 @@
+package com.baeldung.datetime;
+
+import java.time.LocalDateTime;
+import java.time.ZoneId;
+import java.util.Calendar;
+import java.util.Date;
+
+public class UseToInstant {
+    
+    public LocalDateTime convertDateToLocalDate(Date date){
+        LocalDateTime localDateTime = LocalDateTime.ofInstant(date.toInstant(), ZoneId.systemDefault());
+        return localDateTime;
+    }
+    
+    public LocalDateTime convertDateToLocalDate(Calendar calendar){
+        LocalDateTime localDateTime = LocalDateTime.ofInstant(calendar.toInstant(), ZoneId.systemDefault());
+        return localDateTime;
+    }
+}

core-java/src/main/java/com/baeldung/datetime/UseZonedDateTime.java

@@ -0,0 +1,13 @@
+package com.baeldung.datetime;
+
+import java.time.LocalDateTime;
+import java.time.ZoneId;
+import java.time.ZonedDateTime;
+
+public class UseZonedDateTime {
+    
+    public ZonedDateTime getZonedDateTime(LocalDateTime localDateTime,ZoneId zoneId){        
+        ZonedDateTime zonedDateTime = ZonedDateTime.of(localDateTime, zoneId);
+        return zonedDateTime;
+    }
+}

core-java/src/main/java/com/baeldung/doublecolon/Computer.java

@@ -0,0 +1,88 @@
+package com.baeldung.doublecolon;
+
+public class Computer {
+
+    private Integer age;
+    private String color;
+    private Integer healty;
+
+    public Computer(final int age, final String color) {
+        this.age = age;
+        this.color = color;
+    }
+
+    public Computer(final Integer age, final String color, final Integer healty) {
+        this.age = age;
+        this.color = color;
+        this.healty = healty;
+    }
+
+    public Computer() {
+    }
+
+    public Integer getAge() {
+        return age;
+    }
+
+    public void setAge(final Integer age) {
+        this.age = age;
+    }
+
+    public String getColor() {
+        return color;
+    }
+
+    public void setColor(final String color) {
+        this.color = color;
+    }
+
+    public Integer getHealty() {
+        return healty;
+    }
+
+    public void setHealty(final Integer healty) {
+        this.healty = healty;
+    }
+
+    public void turnOnPc() {
+        System.out.println("Computer turned on");
+    }
+
+    public void turnOffPc() {
+        System.out.println("Computer turned off");
+    }
+
+    public Double calculateValue(Double initialValue) {
+        return initialValue / 1.50;
+    }
+
+    @Override
+    public String toString() {
+        return "Computer{" + "age=" + age + ", color='" + color + '\'' + ", healty=" + healty + '}';
+    }
+
+    @Override
+    public boolean equals(final Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+
+        final Computer computer = (Computer) o;
+
+        if (age != null ? !age.equals(computer.age) : computer.age != null) {
+            return false;
+        }
+        return color != null ? color.equals(computer.color) : computer.color == null;
+
+    }
+
+    @Override
+    public int hashCode() {
+        int result = age != null ? age.hashCode() : 0;
+        result = 31 * result + (color != null ? color.hashCode() : 0);
+        return result;
+    }
+}

core-java/src/main/java/com/baeldung/doublecolon/ComputerUtils.java

@@ -0,0 +1,27 @@
+package com.baeldung.doublecolon;
+
+import com.baeldung.doublecolon.function.ComputerPredicate;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class ComputerUtils {
+
+    public static final ComputerPredicate after2010Predicate = (c) -> (c.getAge() > 2010);
+    public static final ComputerPredicate blackPredicate = (c) -> "black".equals(c.getColor());
+
+    public static List<Computer> filter(final List<Computer> inventory, final ComputerPredicate p) {
+
+        final List<Computer> result = new ArrayList<>();
+        inventory.stream().filter(p::filter).forEach(result::add);
+
+        return result;
+    }
+
+    public static void repair(final Computer computer) {
+        if (computer.getHealty() < 50) {
+            computer.setHealty(100);
+        }
+    }
+
+}

core-java/src/main/java/com/baeldung/doublecolon/MacbookPro.java

@@ -0,0 +1,34 @@
+package com.baeldung.doublecolon;
+
+import java.util.function.Function;
+
+public class MacbookPro extends Computer {
+
+    public MacbookPro(int age, String color) {
+        super(age, color);
+    }
+
+    public MacbookPro(Integer age, String color, Integer healty) {
+        super(age, color, healty);
+    }
+
+    @Override
+    public void turnOnPc() {
+        System.out.println("MacbookPro turned on");
+    }
+
+    @Override
+    public void turnOffPc() {
+        System.out.println("MacbookPro turned off");
+    }
+
+    @Override
+    public Double calculateValue(Double initialValue) {
+
+        Function<Double, Double> function = super::calculateValue;
+        final Double pcValue = function.apply(initialValue);
+        System.out.println("First value is:" + pcValue);
+        return pcValue + (initialValue / 10);
+
+    }
+}

core-java/src/main/java/com/baeldung/doublecolon/function/ComputerPredicate.java

@@ -0,0 +1,10 @@
+package com.baeldung.doublecolon.function;
+
+import com.baeldung.doublecolon.Computer;
+
+@FunctionalInterface
+public interface ComputerPredicate {
+
+    boolean filter(Computer c);
+
+}

core-java/src/main/java/com/baeldung/doublecolon/function/TriFunction.java

@@ -0,0 +1,15 @@
+package com.baeldung.doublecolon.function;
+
+import java.util.Objects;
+import java.util.function.Function;
+
+@FunctionalInterface
+public interface TriFunction<A, B, C, R> {
+
+    R apply(A a, B b, C c);
+
+    default <V> TriFunction<A, B, C, V> andThen(final Function<? super R, ? extends V> after) {
+        Objects.requireNonNull(after);
+        return (final A a, final B b, final C c) -> after.apply(apply(a, b, c));
+    }
+}

core-java/src/main/java/com/baeldung/enums/Pizza.java

@@ -1,11 +1,5 @@
 package com.baeldung.enums;
 
-import com.fasterxml.jackson.annotation.JsonFormat;
-import com.fasterxml.jackson.annotation.JsonProperty;
-import com.fasterxml.jackson.databind.ObjectMapper;
-import org.apache.commons.collections15.Predicate;
-
-import java.io.IOException;
 import java.util.EnumMap;
 import java.util.EnumSet;
 import java.util.List;
@@ -13,13 +7,12 @@ import java.util.stream.Collectors;
 
 public class Pizza {
 
-    private static EnumSet<PizzaStatus> undeliveredPizzaStatuses =
-            EnumSet.of(PizzaStatus.ORDERED, PizzaStatus.READY);
+    private static EnumSet<PizzaStatusEnum> deliveredPizzaStatuses =
+            EnumSet.of(PizzaStatusEnum.DELIVERED);
 
-    private PizzaStatus status;
+    private PizzaStatusEnum status;
 
-    @JsonFormat(shape = JsonFormat.Shape.OBJECT)
-    public enum PizzaStatus {
+    public enum PizzaStatusEnum {
         ORDERED(5) {
             @Override
             public boolean isOrdered() {
@@ -53,21 +46,20 @@ public class Pizza {
             return false;
         }
 
-        @JsonProperty("timeToDelivery")
         public int getTimeToDelivery() {
             return timeToDelivery;
         }
 
-        PizzaStatus(int timeToDelivery) {
+        PizzaStatusEnum(int timeToDelivery) {
             this.timeToDelivery = timeToDelivery;
         }
     }
 
-    public PizzaStatus getStatus() {
+    public PizzaStatusEnum getStatus() {
         return status;
     }
 
-    public void setStatus(PizzaStatus status) {
+    public void setStatus(PizzaStatusEnum status) {
         this.status = status;
     }
 
@@ -80,31 +72,20 @@ public class Pizza {
     }
 
     public static List<Pizza> getAllUndeliveredPizzas(List<Pizza> input) {
-        return input.stream().filter(
-                (s) -> undeliveredPizzaStatuses.contains(s.getStatus()))
-                .collect(Collectors.toList());
+        return input.stream().filter((s) -> !deliveredPizzaStatuses.contains(s.getStatus())).collect(Collectors.toList());
     }
 
-    public static EnumMap<PizzaStatus, List<Pizza>>
-    groupPizzaByStatus(List<Pizza> pzList) {
+    public static EnumMap<PizzaStatusEnum, List<Pizza>> groupPizzaByStatus(List<Pizza> pzList) {
         return pzList.stream().collect(
                 Collectors.groupingBy(Pizza::getStatus,
-                        () -> new EnumMap<>(PizzaStatus.class), Collectors.toList()));
+                        () -> new EnumMap<>(PizzaStatusEnum.class), Collectors.toList()));
     }
 
     public void deliver() {
         if (isDeliverable()) {
             PizzaDeliverySystemConfiguration.getInstance().getDeliveryStrategy().deliver(this);
-            this.setStatus(PizzaStatus.DELIVERED);
+            this.setStatus(PizzaStatusEnum.DELIVERED);
         }
     }
 
-    public static String getJsonString(Pizza pz) throws IOException {
-        ObjectMapper mapper = new ObjectMapper();
-        return mapper.writerWithDefaultPrettyPrinter().writeValueAsString(pz);
-    }
-
-    private static Predicate<Pizza> thatAreNotDelivered() {
-        return entry -> undeliveredPizzaStatuses.contains(entry.getStatus());
-    }
 }

core-java/src/main/java/com/baeldung/enums/PizzaDeliverySystemConfiguration.java

@@ -1,5 +1,6 @@
 package com.baeldung.enums;
 
+
 public enum PizzaDeliverySystemConfiguration {
     INSTANCE;
 

core-java/src/main/java/com/baeldung/enums/README.md

@@ -0,0 +1,2 @@
+### Relevant Articles:
+- [A Guide to Java Enums](http://www.baeldung.com/a-guide-to-java-enums)

core-java/src/main/java/com/baeldung/forkjoin/CustomRecursiveAction.java

@@ -0,0 +1,49 @@
+package com.baeldung.forkjoin;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.concurrent.ForkJoinTask;
+import java.util.concurrent.RecursiveAction;
+import java.util.logging.Logger;
+
+public class CustomRecursiveAction extends RecursiveAction {
+
+    private String workLoad = "";
+    private static final int THRESHOLD = 4;
+
+    private static Logger logger = Logger.getAnonymousLogger();
+
+    public CustomRecursiveAction(String workLoad) {
+        this.workLoad = workLoad;
+    }
+
+    @Override
+    protected void compute() {
+
+        if (workLoad.length() > THRESHOLD) {
+            ForkJoinTask.invokeAll(createSubtasks());
+        } else {
+            processing(workLoad);
+        }
+    }
+
+    private Collection<CustomRecursiveAction> createSubtasks() {
+
+        List<CustomRecursiveAction> subtasks =
+                new ArrayList<>();
+
+        String partOne = workLoad.substring(0, workLoad.length() / 2);
+        String partTwo = workLoad.substring(workLoad.length() / 2, workLoad.length());
+
+        subtasks.add(new CustomRecursiveAction(partOne));
+        subtasks.add(new CustomRecursiveAction(partTwo));
+
+        return subtasks;
+    }
+
+    private void processing(String work) {
+        String result = work.toUpperCase();
+        logger.info("This result - (" + result + ") - was processed by " + Thread.currentThread().getName());
+    }
+}

core-java/src/main/java/com/baeldung/forkjoin/CustomRecursiveTask.java

@@ -0,0 +1,51 @@
+package com.baeldung.forkjoin;
+
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.List;
+import java.util.concurrent.ForkJoinTask;
+import java.util.concurrent.RecursiveTask;
+
+public class CustomRecursiveTask extends RecursiveTask<Integer> {
+
+    private int[] arr;
+
+    private static final int THRESHOLD = 20;
+
+    public CustomRecursiveTask(int[] arr) {
+        this.arr = arr;
+    }
+
+    @Override
+    protected Integer compute() {
+
+        if (arr.length > THRESHOLD) {
+
+            return ForkJoinTask.invokeAll(createSubtasks())
+                    .stream()
+                    .mapToInt(ForkJoinTask::join)
+                    .sum();
+
+        } else {
+            return processing(arr);
+        }
+    }
+
+    private Collection<CustomRecursiveTask> createSubtasks() {
+        List<CustomRecursiveTask> dividedTasks = new ArrayList<>();
+        dividedTasks.add(new CustomRecursiveTask(
+                Arrays.copyOfRange(arr, 0, arr.length / 2)));
+        dividedTasks.add(new CustomRecursiveTask(
+                Arrays.copyOfRange(arr, arr.length / 2, arr.length)));
+        return dividedTasks;
+    }
+
+    private Integer processing(int[] arr) {
+        return Arrays.stream(arr)
+                .filter(a -> a > 10 && a < 27)
+                .map(a -> a * 10)
+                .sum();
+    }
+}

core-java/src/main/java/com/baeldung/forkjoin/util/PoolUtil.java

@@ -0,0 +1,10 @@
+package com.baeldung.forkjoin.util;
+
+
+import java.util.concurrent.ForkJoinPool;
+
+public class PoolUtil {
+
+    public static ForkJoinPool forkJoinPool = new ForkJoinPool(2);
+
+}

core-java/src/main/java/com/baeldung/java_8_features/Address.java

@@ -0,0 +1,14 @@
+package com.baeldung.java_8_features;
+
+public class Address {
+
+    private String street;
+
+    public String getStreet() {
+        return street;
+    }
+
+    public void setStreet(String street) {
+        this.street = street;
+    }
+}

core-java/src/main/java/com/baeldung/java_8_features/CustomException.java

@@ -0,0 +1,4 @@
+package com.baeldung.java_8_features;
+
+public class CustomException extends RuntimeException {
+}

core-java/src/main/java/com/baeldung/java_8_features/Detail.java

@@ -0,0 +1,13 @@
+package com.baeldung.java_8_features;
+
+import java.util.Arrays;
+import java.util.List;
+
+public class Detail {
+
+    private static final List<String> PARTS = Arrays.asList("turbine", "pump");
+
+    public List<String> getParts() {
+        return PARTS;
+    }
+}

core-java/src/main/java/com/baeldung/java_8_features/OptionalAddress.java

@@ -0,0 +1,16 @@
+package com.baeldung.java_8_features;
+
+import java.util.Optional;
+
+public class OptionalAddress {
+
+    private String street;
+
+    public Optional<String> getStreet() {
+        return Optional.ofNullable(street);
+    }
+
+    public void setStreet(String street) {
+        this.street = street;
+    }
+}

core-java/src/main/java/com/baeldung/java_8_features/OptionalUser.java

@@ -0,0 +1,16 @@
+package com.baeldung.java_8_features;
+
+import java.util.Optional;
+
+public class OptionalUser {
+
+    private OptionalAddress address;
+
+    public Optional<OptionalAddress> getAddress() {
+        return Optional.of(address);
+    }
+
+    public void setAddress(OptionalAddress address) {
+        this.address = address;
+    }
+}

core-java/src/main/java/com/baeldung/java_8_features/User.java

@@ -0,0 +1,40 @@
+package com.baeldung.java_8_features;
+
+import java.util.Optional;
+
+public class User {
+
+    private String name;
+
+    private Address address;
+
+    public Address getAddress() {
+        return address;
+    }
+
+    public void setAddress(Address address) {
+        this.address = address;
+    }
+
+    public User() {
+    }
+
+    public User(String name) {
+        this.name = name;
+    }
+
+    public static boolean isRealUser(User user) {
+        return true;
+    }
+
+    public String getOrThrow() {
+        String value = null;
+        Optional<String> valueOpt = Optional.ofNullable(value);
+        String result = valueOpt.orElseThrow(CustomException::new).toUpperCase();
+        return result;
+    }
+
+    public boolean isLegalName(String name) {
+        return name.length() > 3 && name.length() < 16;
+    }
+}

core-java/src/main/java/com/baeldung/java_8_features/Vehicle.java

@@ -0,0 +1,18 @@
+package com.baeldung.java_8_features;
+
+public interface Vehicle {
+
+    void moveTo(long altitude, long longitude);
+
+    static String producer() {
+        return "N&F Vehicles";
+    }
+
+    default long[] startPosition() {
+        return new long[]{23, 15};
+    }
+
+    default String getOverview() {
+        return "ATV made by " + producer();
+    }
+}

core-java/src/main/java/com/baeldung/java_8_features/VehicleImpl.java

@@ -0,0 +1,9 @@
+package com.baeldung.java_8_features;
+
+public class VehicleImpl implements  Vehicle {
+
+    @Override
+    public void moveTo(long altitude, long longitude) {
+        //do nothing
+    }
+}

core-java/src/main/java/com/baeldung/streamApi/Product.java

@@ -0,0 +1,51 @@
+package com.baeldung.streamApi;
+
+import java.util.List;
+import java.util.Optional;
+import java.util.stream.IntStream;
+import java.util.stream.Stream;
+
+/**
+ * Created by Alex Vengr
+ */
+public class Product {
+
+    private int price;
+
+    private String name;
+
+    private boolean utilize;
+
+    public Product(int price, String name) {
+        this(price);
+        this.name = name;
+    }
+
+    public Product(int price) {
+        this.price = price;
+    }
+
+    public Product() {
+    }
+
+    public int getPrice() {
+        return price;
+    }
+
+    public void setPrice(int price) {
+        this.price = price;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+
+    public static Stream<String> streamOf(List<String> list) {
+        return (list == null || list.isEmpty()) ? Stream.empty() : list.stream();
+    }
+}

core-java/src/main/java/com/baeldung/threadpool/CountingTask.java

@@ -0,0 +1,22 @@
+package com.baeldung.threadpool;
+
+import java.util.concurrent.ForkJoinTask;
+import java.util.concurrent.RecursiveTask;
+import java.util.stream.Collectors;
+
+public class CountingTask extends RecursiveTask<Integer> {
+
+    private final TreeNode node;
+
+    public CountingTask(TreeNode node) {
+        this.node = node;
+    }
+
+    @Override
+    protected Integer compute() {
+        return node.value + node.children.stream()
+                .map(childNode -> new CountingTask(childNode).fork())
+                .collect(Collectors.summingInt(ForkJoinTask::join));
+    }
+
+}

core-java/src/main/java/com/baeldung/threadpool/ExitingExecutorServiceExample.java

@@ -0,0 +1,29 @@
+package com.baeldung.threadpool;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
+
+import com.google.common.util.concurrent.MoreExecutors;
+
+/**
+ * This class demonstrates the usage of Guava's exiting executor services that keep the VM from hanging.
+ * Without the exiting executor service, the task would hang indefinitely.
+ * This behaviour cannot be demonstrated in JUnit tests, as JUnit kills the VM after the tests.
+ */
+public class ExitingExecutorServiceExample {
+
+    public static void main(String... args) {
+
+        ThreadPoolExecutor executor = (ThreadPoolExecutor) Executors.newFixedThreadPool(5);
+        ExecutorService executorService = MoreExecutors.getExitingExecutorService(executor, 100, TimeUnit.MILLISECONDS);
+
+        executorService.submit(() -> {
+            while (true) {
+            }
+        });
+
+    }
+
+}

core-java/src/main/java/com/baeldung/threadpool/TreeNode.java

@@ -0,0 +1,18 @@
+package com.baeldung.threadpool;
+
+import java.util.Set;
+
+import com.google.common.collect.Sets;
+
+public class TreeNode {
+
+    int value;
+
+    Set<TreeNode> children;
+
+    public TreeNode(int value, TreeNode... children) {
+        this.value = value;
+        this.children = Sets.newHashSet(children);
+    }
+
+}

core-java/src/main/java/com/baeldung/unzip/UnzipFile.java

@@ -0,0 +1,30 @@
+package com.baeldung.unzip;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.util.zip.ZipEntry;
+import java.util.zip.ZipInputStream;
+
+public class UnzipFile {
+    public static void main(final String[] args) throws IOException {
+        final String fileZip = "src/main/resources/compressed.zip";
+        final byte[] buffer = new byte[1024];
+        final ZipInputStream zis = new ZipInputStream(new FileInputStream(fileZip));
+        ZipEntry zipEntry = zis.getNextEntry();
+        while (zipEntry != null) {
+            final String fileName = zipEntry.getName();
+            final File newFile = new File("src/main/resources/unzipTest/" + fileName);
+            final FileOutputStream fos = new FileOutputStream(newFile);
+            int len;
+            while ((len = zis.read(buffer)) > 0) {
+                fos.write(buffer, 0, len);
+            }
+            fos.close();
+            zipEntry = zis.getNextEntry();
+        }
+        zis.closeEntry();
+        zis.close();
+    }
+}

core-java/src/main/java/com/baeldung/zip/ZipDirectory.java

@@ -0,0 +1,43 @@
+package com.baeldung.zip;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.util.zip.ZipEntry;
+import java.util.zip.ZipOutputStream;
+
+public class ZipDirectory {
+    public static void main(final String[] args) throws IOException {
+        final String sourceFile = "src/main/resources/zipTest";
+        final FileOutputStream fos = new FileOutputStream("src/main/resources/dirCompressed.zip");
+        final ZipOutputStream zipOut = new ZipOutputStream(fos);
+        final File fileToZip = new File(sourceFile);
+
+        zipFile(fileToZip, fileToZip.getName(), zipOut);
+        zipOut.close();
+        fos.close();
+    }
+
+    private static void zipFile(final File fileToZip, final String fileName, final ZipOutputStream zipOut) throws IOException {
+        if (fileToZip.isHidden()) {
+            return;
+        }
+        if (fileToZip.isDirectory()) {
+            final File[] children = fileToZip.listFiles();
+            for (final File childFile : children) {
+                zipFile(childFile, fileName + "/" + childFile.getName(), zipOut);
+            }
+            return;
+        }
+        final FileInputStream fis = new FileInputStream(fileToZip);
+        final ZipEntry zipEntry = new ZipEntry(fileName);
+        zipOut.putNextEntry(zipEntry);
+        final byte[] bytes = new byte[1024];
+        int length;
+        while ((length = fis.read(bytes)) >= 0) {
+            zipOut.write(bytes, 0, length);
+        }
+        fis.close();
+    }
+}

core-java/src/main/java/com/baeldung/zip/ZipFile.java

@@ -0,0 +1,28 @@
+package com.baeldung.zip;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.util.zip.ZipEntry;
+import java.util.zip.ZipOutputStream;
+
+public class ZipFile {
+    public static void main(final String[] args) throws IOException {
+        final String sourceFile = "src/main/resources/zipTest/test1.txt";
+        final FileOutputStream fos = new FileOutputStream("src/main/resources/compressed.zip");
+        final ZipOutputStream zipOut = new ZipOutputStream(fos);
+        final File fileToZip = new File(sourceFile);
+        final FileInputStream fis = new FileInputStream(fileToZip);
+        final ZipEntry zipEntry = new ZipEntry(fileToZip.getName());
+        zipOut.putNextEntry(zipEntry);
+        final byte[] bytes = new byte[1024];
+        int length;
+        while ((length = fis.read(bytes)) >= 0) {
+            zipOut.write(bytes, 0, length);
+        }
+        zipOut.close();
+        fis.close();
+        fos.close();
+    }
+}

core-java/src/main/java/com/baeldung/zip/ZipMultipleFiles.java

@@ -0,0 +1,33 @@
+package com.baeldung.zip;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.List;
+import java.util.zip.ZipEntry;
+import java.util.zip.ZipOutputStream;
+
+public class ZipMultipleFiles {
+    public static void main(final String[] args) throws IOException {
+        final List<String> srcFiles = Arrays.asList("src/main/resources/zipTest/test1.txt", "src/main/resources/zipTest/test2.txt");
+        final FileOutputStream fos = new FileOutputStream("src/main/resources/multiCompressed.zip");
+        final ZipOutputStream zipOut = new ZipOutputStream(fos);
+        for (final String srcFile : srcFiles) {
+            final File fileToZip = new File(srcFile);
+            final FileInputStream fis = new FileInputStream(fileToZip);
+            final ZipEntry zipEntry = new ZipEntry(fileToZip.getName());
+            zipOut.putNextEntry(zipEntry);
+
+            final byte[] bytes = new byte[1024];
+            int length;
+            while ((length = fis.read(bytes)) >= 0) {
+                zipOut.write(bytes, 0, length);
+            }
+            fis.close();
+        }
+        zipOut.close();
+        fos.close();
+    }
+}

core-java/src/test/java/com/baeldung/dateapi/ConversionExample.java

@@ -0,0 +1,19 @@
+package com.baeldung.dateapi;
+
+import java.time.Instant;
+import java.time.ZoneId;
+import java.time.ZonedDateTime;
+import java.util.Date;
+import java.util.GregorianCalendar;
+import java.util.TimeZone;
+
+public class ConversionExample {
+    public static void main(String[] args) {
+        Instant instantFromCalendar = GregorianCalendar.getInstance().toInstant();
+        ZonedDateTime zonedDateTimeFromCalendar = new GregorianCalendar().toZonedDateTime();
+        Date dateFromInstant = Date.from(Instant.now());
+        GregorianCalendar calendarFromZonedDateTime = GregorianCalendar.from(ZonedDateTime.now());
+        Instant instantFromDate = new Date().toInstant();
+        ZoneId zoneIdFromTimeZone = TimeZone.getTimeZone("PST").toZoneId();
+    }
+}

core-java/src/test/java/com/baeldung/dateapi/JavaUtilTimeTest.java

@@ -0,0 +1,89 @@
+package com.baeldung.dateapi;
+
+import org.junit.Test;
+
+import java.text.ParseException;
+import java.time.Duration;
+import java.time.LocalDate;
+import java.time.LocalDateTime;
+import java.time.LocalTime;
+import java.time.Month;
+import java.time.YearMonth;
+import java.time.format.DateTimeFormatter;
+import java.time.temporal.ChronoUnit;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class JavaUtilTimeTest {
+
+    @Test
+    public void currentTime() {
+        final LocalDate now = LocalDate.now();
+
+        System.out.println(now);
+        // there is not much to test here
+    }
+
+    @Test
+    public void specificTime() {
+        LocalDate birthDay = LocalDate.of(1990, Month.DECEMBER, 15);
+
+        System.out.println(birthDay);
+        // there is not much to test here
+    }
+
+    @Test
+    public void extractMonth() {
+        Month month = LocalDate.of(1990, Month.DECEMBER, 15).getMonth();
+
+        assertThat(month).isEqualTo(Month.DECEMBER);
+    }
+
+    @Test
+    public void subtractTime() {
+        LocalDateTime fiveHoursBefore = LocalDateTime.of(1990, Month.DECEMBER, 15, 15, 0).minusHours(5);
+
+        assertThat(fiveHoursBefore.getHour()).isEqualTo(10);
+    }
+
+    @Test
+    public void alterField() {
+        LocalDateTime inJune = LocalDateTime.of(1990, Month.DECEMBER, 15, 15, 0).with(Month.JUNE);
+
+        assertThat(inJune.getMonth()).isEqualTo(Month.JUNE);
+    }
+
+    @Test
+    public void truncate() {
+        LocalTime truncated = LocalTime.of(15, 12, 34).truncatedTo(ChronoUnit.HOURS);
+
+        assertThat(truncated).isEqualTo(LocalTime.of(15, 0, 0));
+    }
+
+    @Test
+    public void getTimeSpan() {
+        LocalDateTime now = LocalDateTime.now();
+        LocalDateTime hourLater = now.plusHours(1);
+        Duration span = Duration.between(now, hourLater);
+
+        assertThat(span).isEqualTo(Duration.ofHours(1));
+    }
+
+    @Test
+    public void formatAndParse() throws ParseException {
+        LocalDate someDate = LocalDate.of(2016, 12, 7);
+        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");
+        String formattedDate = someDate.format(formatter);
+        LocalDate parsedDate = LocalDate.parse(formattedDate, formatter);
+
+        assertThat(formattedDate).isEqualTo("2016-12-07");
+        assertThat(parsedDate).isEqualTo(someDate);
+    }
+
+    @Test
+    public void daysInMonth() {
+        int daysInMonth = YearMonth.of(1990, 2).lengthOfMonth();
+
+        assertThat(daysInMonth).isEqualTo(28);
+    }
+}