BAEL-2524 (#6206)

* BAEL-2524

Uploading article examples.

* Fixing build error

Used List.of, which is not available on java 8 (running java 11 on my PC)

core-java-8/src/test/java/com/baeldung/java8/lambda/methodreference/Bicycle.java

@@ -0,0 +1,29 @@
+package com.baeldung.java8.lambda.methodreference;
+
+public class Bicycle {
+
+    private String brand;
+    private Integer frameSize;
+
+    public Bicycle(String brand, Integer frameSize) {
+        this.brand = brand;
+        this.frameSize = frameSize;
+    }
+
+    public String getBrand() {
+        return brand;
+    }
+
+    public void setBrand(String brand) {
+        this.brand = brand;
+    }
+
+    public Integer getFrameSize() {
+        return frameSize;
+    }
+
+    public void setFrameSize(Integer frameSize) {
+        this.frameSize = frameSize;
+    }
+
+}

core-java-8/src/test/java/com/baeldung/java8/lambda/methodreference/BicycleComparator.java

@@ -0,0 +1,13 @@
+package com.baeldung.java8.lambda.methodreference;
+
+import java.util.Comparator;
+
+public class BicycleComparator implements Comparator<Bicycle> {
+
+    @Override
+    public int compare(Bicycle a, Bicycle b) {
+        return a.getFrameSize()
+            .compareTo(b.getFrameSize());
+    }
+
+}

core-java-8/src/test/java/com/baeldung/java8/lambda/methodreference/MethodReferenceExamples.java

@@ -0,0 +1,70 @@
+package com.baeldung.java8.lambda.methodreference;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.function.BiFunction;
+
+import org.junit.Test;
+
+public class MethodReferenceExamples {
+
+    private static <T> void doNothingAtAll(Object... o) {
+    }
+
+    ;
+
+    @Test
+    public void referenceToStaticMethod() {
+        List<String> messages = Arrays.asList("Hello", "Baeldung", "readers!");
+        messages.forEach((word) -> {
+            System.out.println(word);
+        });
+        messages.forEach(System.out::println);
+    }
+
+    @Test
+    public void referenceToInstanceMethodOfParticularObject() {
+        BicycleComparator bikeFrameSizeComparator = new BicycleComparator();
+        createBicyclesList().stream()
+            .sorted((a, b) -> bikeFrameSizeComparator.compare(a, b));
+        createBicyclesList().stream()
+            .sorted(bikeFrameSizeComparator::compare);
+    }
+
+    @Test
+    public void referenceToInstanceMethodOfArbitratyObjectOfParticularType() {
+        List<Integer> numbers = Arrays.asList(5, 3, 50, 24, 40, 2, 9, 18);
+        numbers.stream()
+            .sorted((a, b) -> Integer.compare(a, b));
+        numbers.stream()
+            .sorted(Integer::compare);
+    }
+
+    @Test
+    public void referenceToConstructor() {
+        BiFunction<String, Integer, Bicycle> bikeCreator = (brand, frameSize) -> new Bicycle(brand, frameSize);
+        BiFunction<String, Integer, Bicycle> bikeCreatorMethodReference = Bicycle::new;
+        List<Bicycle> bikes = new ArrayList<>();
+        bikes.add(bikeCreator.apply("Giant", 50));
+        bikes.add(bikeCreator.apply("Scott", 20));
+        bikes.add(bikeCreatorMethodReference.apply("Trek", 35));
+        bikes.add(bikeCreatorMethodReference.apply("GT", 40));
+    }
+
+    @Test
+    public void limitationsAndAdditionalExamples() {
+        createBicyclesList().forEach(b -> System.out.printf("Bike brand is '%s' and frame size is '%d'%n", b.getBrand(), b.getFrameSize()));
+        createBicyclesList().forEach((o) -> this.doNothingAtAll(o));
+    }
+
+    private List<Bicycle> createBicyclesList() {
+        List<Bicycle> bikes = new ArrayList<>();
+        bikes.add(new Bicycle("Giant", 50));
+        bikes.add(new Bicycle("Scott", 20));
+        bikes.add(new Bicycle("Trek", 35));
+        bikes.add(new Bicycle("GT", 40));
+        return bikes;
+    }
+
+}