BeforeJava11Lambda.java

// Any local variable declaration
List<String> list = new ArrayList<String>();
Stream<String> stream = getStream()
// For Lambda Expression.
(String a, String b) -> a.concat(b)

HTTPClientJava11.java

HttpClient client = HttpClient.newHttpClient();
HttpRequest request = HttpRequest.newBuilder()
      .uri(URI.create("http://openjdk.java.net/"))
      .build();
client.sendAsync(request, BodyHandlers.ofString())
      .thenApply(HttpResponse::body)
      .thenAccept(System.out::println)
      .join();

IntroToJava11And12.java

public class HelloUniverse{
    public static void main(String[] args) {
        System.out.println("Hello InfoQ Universe");
    }
}


/**
* Before Java 11:
* Compile:$javac HelloUniverse.java
* Run:$java HelloUniverse
* O/p:Hello InfoQ Universe
* In Java 11:
* Run:$java HelloUniverse.java
* O/p:Hello InfoQ Universe
*/

Java12Changes.java

public static void main(String[] args) {
    List<Employee> employeeList = Arrays.asList(
            new Employee(1, "A", 100),
            new Employee(2, "B", 200),
            new Employee(3, "C", 300),
            new Employee(4, "D", 400));

    HashMap<String, Employee> result = employeeList.stream().collect(
            Collectors.teeing(
                    Collectors.maxBy(Comparator.comparing(Employee::getSalary)),
                    Collectors.minBy(Comparator.comparing(Employee::getSalary)),
                    (e1, e2) -> {
                        HashMap<String, Employee> map = new HashMap();
                        map.put("MAX", e1.get());
                        map.put("MIN", e2.get());
                        return map;
                    }
            ));

    System.out.println(result);
}

JVMMicroBenchMark.java

import org.openjdk.jmh.annotations.Benchmark;
public class MyBenchmark {
    @Benchmark
    public void testMethod() {
        // This is a demo/sample template for building your JMH benchmarks. Edit as needed.
        // Put your benchmark code here.
        int a = 1;
        int b = 2;
        int sum = a + b;
    }
}

NewSwitchExpression.java

public String getTextViaArrow(int number) {
        String result = switch (number) {
            case 1, 2 -> "one or two";
            case 3 -> "three";
            case 4, 5, 6 -> "four or five or six";
            default -> "unknown";
        };
        return result;
}


# Note: Its preview feature and not going to run in your ide directly.
# Follow below steps to run.
# $javac --enable-preview --release 13 SwitchExpression.java
# $ java --ennable-preview SwitchExpression

OldSwitchExpression.java

public String getTextViaBreak(int number) {
        String result = switch (number) {
            case 1:
            case 2:
                break "one or two"; 
            case 3:
                break "three";
            case 4:
            case 5:
            case 6:
                break "four or five or six";
            default:
                break "unknown";
        };
        return result;
    }

ScriptingUsingJava.java

./listallfiles
#!/usr/bin/java --source 11
import java.nio.file.*;
public class ListFiles {
public static void main (String ... args) throws Exception
{
Files.walk(Path.get(args[0]))
.forEaach(System.out::println);
 }
}
How to Run:
$chmod +x listallfiles
$./listallfiles .  // Here "." is a current directory.

WithLambda11.java

// Any local variable declaration.
var list = new ArrayList<String>();
var stream = getStream();
// For Lambda Expression.
(var a, var b) -> a.concat(b)