[BAEL-13506] - Split or move core-java-8 module (#7790)

core-java-modules/core-java-lambdas/README.md

@@ -6,3 +6,4 @@
 - [Lambda Expressions and Functional Interfaces: Tips and Best Practices](http://www.baeldung.com/java-8-lambda-expressions-tips)
 - [Exceptions in Java 8 Lambda Expressions](http://www.baeldung.com/java-lambda-exceptions)
 - [Method References in Java](https://www.baeldung.com/java-method-references)
+- [The Double Colon Operator in Java 8](https://www.baeldung.com/java-8-double-colon-operator)

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

@@ -0,0 +1,85 @@
+package com.baeldung.doublecolon;
+
+public class Computer {
+
+    private Integer age;
+    private String color;
+    private Integer healty;
+
+    Computer(final int age, final String color) {
+        this.age = age;
+        this.color = color;
+    }
+
+    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;
+    }
+
+    String getColor() {
+        return color;
+    }
+
+    public void setColor(final String color) {
+        this.color = color;
+    }
+
+    Integer getHealty() {
+        return healty;
+    }
+
+    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;
+
+        return (age != null ? age.equals(computer.age) : computer.age == null) && (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-modules/core-java-lambdas/src/main/java/com/baeldung/doublecolon/ComputerUtils.java

@@ -0,0 +1,27 @@
+package com.baeldung.doublecolon;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import com.baeldung.doublecolon.function.ComputerPredicate;
+
+public class ComputerUtils {
+
+    static final ComputerPredicate after2010Predicate = (c) -> (c.getAge() > 2010);
+    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;
+    }
+
+    static void repair(final Computer computer) {
+        if (computer.getHealty() < 50) {
+            computer.setHealty(100);
+        }
+    }
+
+}

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

@@ -0,0 +1,39 @@
+package com.baeldung.doublecolon;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.function.Function;
+
+public class MacbookPro extends Computer {
+
+    private static final Logger LOG = LoggerFactory.getLogger(MacbookPro.class);
+
+    public MacbookPro(int age, String color) {
+        super(age, color);
+    }
+
+    MacbookPro(Integer age, String color, Integer healty) {
+        super(age, color, healty);
+    }
+
+    @Override
+    public void turnOnPc() {
+        LOG.debug("MacbookPro turned on");
+    }
+
+    @Override
+    public void turnOffPc() {
+        LOG.debug("MacbookPro turned off");
+    }
+
+    @Override
+    public Double calculateValue(Double initialValue) {
+
+        Function<Double, Double> function = super::calculateValue;
+        final Double pcValue = function.apply(initialValue);
+        LOG.debug("First value is:" + pcValue);
+        return pcValue + (initialValue / 10);
+
+    }
+}

core-java-modules/core-java-lambdas/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-modules/core-java-lambdas/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-modules/core-java-lambdas/src/test/java/com/baeldung/doublecolon/ComputerUtilsUnitTest.java

@@ -0,0 +1,91 @@
+package com.baeldung.doublecolon;
+
+import com.baeldung.doublecolon.function.TriFunction;
+import org.junit.After;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.Comparator;
+import java.util.List;
+import java.util.function.BiFunction;
+
+import static com.baeldung.doublecolon.ComputerUtils.*;
+
+public class ComputerUtilsUnitTest {
+
+    @Before
+    public void setup() {
+    }
+
+    @After
+    public void tearDown() {
+    }
+
+    @Test
+    public void testConstructorReference() {
+
+        Computer c1 = new Computer(2015, "white");
+        Computer c2 = new Computer(2009, "black");
+        Computer c3 = new Computer(2014, "black");
+
+        BiFunction<Integer, String, Computer> c4Function = Computer::new;
+        Computer c4 = c4Function.apply(2013, "white");
+        BiFunction<Integer, String, Computer> c5Function = Computer::new;
+        Computer c5 = c5Function.apply(2010, "black");
+        BiFunction<Integer, String, Computer> c6Function = Computer::new;
+        Computer c6 = c6Function.apply(2008, "black");
+
+        List<Computer> inventory = Arrays.asList(c1, c2, c3, c4, c5, c6);
+
+        List<Computer> blackComputer = filter(inventory, blackPredicate);
+        Assert.assertEquals("The black Computers are: ", blackComputer.size(), 4);
+
+        List<Computer> after2010Computer = filter(inventory, after2010Predicate);
+        Assert.assertEquals("The Computer bought after 2010 are: ", after2010Computer.size(), 3);
+
+        List<Computer> before2011Computer = filter(inventory, c -> c.getAge() < 2011);
+        Assert.assertEquals("The Computer bought before 2011 are: ", before2011Computer.size(), 3);
+
+        inventory.sort(Comparator.comparing(Computer::getAge));
+
+        Assert.assertEquals("Oldest Computer in inventory", c6, inventory.get(0));
+
+    }
+
+    @Test
+    public void testStaticMethodReference() {
+
+        Computer c1 = new Computer(2015, "white", 35);
+        Computer c2 = new Computer(2009, "black", 65);
+        TriFunction<Integer, String, Integer, Computer> c6Function = Computer::new;
+        Computer c3 = c6Function.apply(2008, "black", 90);
+
+        List<Computer> inventory = Arrays.asList(c1, c2, c3);
+        inventory.forEach(ComputerUtils::repair);
+
+        Assert.assertEquals("Computer repaired", new Integer(100), c1.getHealty());
+    }
+
+    @Test
+    public void testInstanceMethodArbitraryObjectParticularType() {
+
+        Computer c1 = new Computer(2015, "white", 35);
+        Computer c2 = new MacbookPro(2009, "black", 65);
+        List<Computer> inventory = Arrays.asList(c1, c2);
+        inventory.forEach(Computer::turnOnPc);
+
+    }
+
+    @Test
+    public void testSuperMethodReference() {
+
+        final TriFunction<Integer, String, Integer, MacbookPro> integerStringIntegerObjectTriFunction = MacbookPro::new;
+        final MacbookPro macbookPro = integerStringIntegerObjectTriFunction.apply(2010, "black", 100);
+        Double initialValue = 999.99;
+        final Double actualValue = macbookPro.calculateValue(initialValue);
+        Assert.assertEquals(766.659, actualValue, 0.0);
+    }
+
+}