public class Test {
    public static void main(String[] args) {
        String str = "abcd";
        System.out.println(str.substring(2));
    }
}

jshell> String str = "abcd";
str ==> "abcd"
jshell> System.out.println(str.substring(2));
cd

> javadoc -sourcepath "/Users/bjjeon/Downloads/src" 
  com.html5doc -d /Users/bjjeon/Downloads/html5doc -html5

    // BufferedReader is declared outside try() block
    BufferedReader br = new BufferedReader(new FileReader("C://readfile/input.txt"));
    try (BufferedReader inBr = br) {
            // ...
        }
    } catch (IOException e) {
        // ...
    }

    // BufferedReader is declared outside try() block
    BufferedReader br = new BufferedReader(new FileReader("C://readfile/input.txt"));

    // Java 9 make it simple
    try (br) {
        String line;
        while (null != (line = br.readLine())) {
            // processing each line of file
            System.out.println(line);
        }
    } catch (IOException e) {
        e.printStackTrace();
    }

    public interface IMyInterface{
     
        private void method1(String arg){
            // do something
        }
     
        private static void method2(Integer arg){
            // do something
        }
    }

        MyHandler<Integer> intHandler = new MyHandler<>(10) {// Anonymous Class };
        MyHandler<?> handler = new MyHandler<>("Onehundred"){// Anonymous Class };

        MyHandler<Integer> intHandler = new MyHandler<>(1){
            @Override
            public void handle(){
            }
        };
         
        MyHandler<? extends Integer> intHandler1 = new MyHandler<>(10){
            @Override
            void handle(){
            }
        };
         
        MyHandler<?> handler = new MyHandler<>("One hundred"){
            @Override
            void handle(){
            }
        };

    // current Process
    ProcessHandle processHandle = ProcessHandle.current();
     
    processHandle.getPid();
    processHandle.isAlive();
    processHandle.children().count();
    processHandle.supportsNormalTermination();

        ProcessHandle.InfoprocessInfo = processHandle.info();
         
        processInfo.arguments();
        processInfo.command();
        processInfo.totalCpuDuration();
        processInfo.user();
         
        // all Processes
        Stream<ProcessHandle> processStream = ProcessHandle.allProcesses();
         
        // destroy Process
        processHandle.destroy();

        package java.lang;

        public class System {
            System.Logger getLogger(String name) { ... }
            System.Logger getLogger(String name, ResourceBundle bundle) { ... }
        }

    delay()
    future.completeAsync(supplier, CompletableFuture.delayedExecutor(3, TimeUnit.SECONDS))

    .thenAccept(result -> System.out.println("accept: " + result));

        orTimeout()

        // TIMEOUT = 3;
        // doWork() takes 5 seconds to finish
 
        CompletableFuture<String> future = 
                doWork("JavaSampleApproach")
                .orTimeout(TIMEOUT, TimeUnit.SECONDS)
                .whenComplete((result, error) -> {
                    if (error == null) {
                        System.out.println("The result is: " + result);
                    } else {
                        System.out.println("Sorry, timeout in " + TIMEOUT + " seconds");
                    }
                });

        completeOnTimeout()

        // TIMEOUT = 3;
        // doWork() takes 5 seconds to finish

        CompletableFuture<String> future = 
                doWork("JavaSampleApproach")
                .completeOnTimeout("JavaTechnology", TIMEOUT, TimeUnit.SECONDS)
                .whenComplete((result, error) -> {
                    if (error == null) {
                        System.out.println("The result is: " + result);
                    } else {
                        // this statement will never run.
                        System.out.println("Sorry, timeout in " + TIMEOUT + " seconds.");
                    }
                });

        List<String> immutableList = List.of("one","two","three");
        Set<String> immutableSet = Set.of("one","two","three");
        Map<Integer,String> immutableMap = Map.of(1,"one",2,"two",3,"three")

    public <T> T walk(Function<? super Stream<StackFrame>, ? extends T> function);
    public void forEach(Consumer<? super StackFrame> action);
    public Class<?> getCallerClass();