Method Reference and Stream, Parallel Streams

Author: arpitaggarwal

src/main/java/com/arpit/java8/method/reference/HelloService.java

@@ -0,0 +1,7 @@
+package com.arpit.java8.method.reference;
+
+@FunctionalInterface
+public interface HelloService {
+
+	void hello();
+}

src/main/java/com/arpit/java8/method/reference/Main.java

@@ -0,0 +1,16 @@
+package com.arpit.java8.method.reference;
+
+public class Main {
+
+	private static void hello() {
+		System.out.println("hello");
+	}
+
+	public static void main(String[] args) {
+		// Referring static method
+		HelloService helloService = Main::hello;
+		// Calling interface method
+		helloService.hello();
+	}
+
+}

src/main/java/com/arpit/java8/streams/StreamAndParallelStream.java

@@ -0,0 +1,32 @@
+package com.arpit.java8.streams;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class StreamAndParallelStream {
+
+	public static void main(String... args) {
+		List<Integer> list = new ArrayList<>();
+		for (int i = 0; i < 1000; i++) {
+			list.add(i);
+		}
+		printUsingStream(list);
+		printUsingParallelStream(list);
+	}
+
+	private static void printUsingStream(List<Integer> list) {
+		list.stream().forEach(System.out::println);
+	}
+
+	/**
+	 * If we change stream() to parallelStream() this is not the case anymore
+	 * all number are written, but in a different order. So, apparently,
+	 * parallelStream() indeed uses multiple threads.
+	 * 
+	 * 
+	 * @param list
+	 */
+	private static void printUsingParallelStream(List<Integer> list) {
+		list.parallelStream().forEach(System.out::println);
+	}
+}