An unnamed module is a concept of the unnamed package. It is a module in which packages or classes can't be defined in any named module but exist in the jar file from classpath. If our code can try to load type from those files, the module system attempts to lookup classpath and loads it.An unnamed module read all other modules, including all of the named,  built-in platform modules, and also exports all of its packages. The package in an unnamed module can be ignored, which is also defined in the named module.The unnamed module has access to:All packages exported by all other modules available in module-path.All the jars ... Read More

Java 9 has improved Process API, and it helps to manage and control operating system processes. Before Java 9, it has been difficult to manage and control operating system processes using Java programs. Since Java 9, new classes and interfaces have added to control the operating system process through Java programs. New interfaces like ProcessHandle and ProcessHandle.Info have added, and also new methods have added to Process class.In the below example, we can traverse a process tree (children and descendant processes) of Process API.Exampleimport java.io.IOException; public class ProcessTreeTest {    public static void main(String args[]) throws IOException {       Runtime.getRuntime().exec("cmd");   ... Read More

Java 9 has added improvements to Process API for getting PID of running process, getting children and/or descendants of a process, and also added a new class that helps to list out all running processes, getting information about an arbitrary process, and traversing process tree. The information returned by these methods can be a snapshot of processes running on the OS.In the below example, we can get an ID of the running process by using the pid() method of ProcessHandle.Examplepublic class ProcessHandleTest {    public static void main(String args[]) {       ProcessHandle processHandle = ProcessHandle.current();       System.out.println("PID of running Process: " + ... Read More

JShell is an interactive tool for learning Java, and it is a REPL(Read-Evaluate-Print-Loop) that evaluates declarations, statements, and expressions.While leaving a JShell session, we want to reuse the code previously entered into a new session. This can be done by using the command: /open [File_Path]. This command will load all code and internal commands found in file[File_Path] supplied as an option.In the below code snippet, we can use the "/open [File_Path]" command to load source code from the directory with the ".jsh" extension.C:\Users\User>jshell | Welcome to JShell -- Version 9.0.4 | For an introduction type: /help intro jshell> ... Read More

An automatic module is a jar that we put on the modulepath. There is a number of pre-existing libraries that can be used in our applications, and many of these are not yet modularized. To facilitate migration, we can add any library’s jar file to an application’s module path, then use packages in that jar file. It can implicitly become an automatic module and can be specified in the module declaration’s requires directive. The jar’s filename becomes its module name that must be a valid Java identifier that can be used in "requires" directive.An automatic module:Implicitly exports all package types, so ... Read More

Java 9 has introduced JShell for Java, and it allows us to evaluate code snippets such as declarations, statements, and expressions.During the JShell session, we need to reset it without closing and re-opening JShell then we can use the internal command: "/reset". By using this command, code entered during the current session has erased. It can be useful when we want to test new classes, create new variables, etc. while keeping the names previously used.In the below snippet, we have created variables x, y, and str. We can able to see all entered code snippets using the "/list" command. After that, we can apply ... Read More

When performing an operation in the JShell tool, it displays a message in return (success of the command, error, and type of a variable created as well as its value). It has been customized using the command: "/set feedback". This command displays the type of return currently configured as well as the different return modes available.jshell> /set feedback | /set feedback normal | | Available feedback modes: | concise | normal | silent | verboseThere are four feedback modes available in JShell as listed below:1) /set feedback normal: This is the default JShell feedback. When we evaluate an expression, JShell returns the corresponding result and an ... Read More

The directory structure of JDK and JRE are almost the same, except that JDK has two additional directories like jmods and include and also there is no JRE subdirectory in the JDK9 version. The JDK directory is the root directory for JDK software installation. This directory also includes copyright, readme, and src.zip files, which can be a source code archive file of the Java platform.JDK Directory Structure:JDK-9    - bin    - conf    - include    - jmods    - legal    - libThe JDK/bin directory contains an executable and command-line launcher that can be defined by the modules linked to an image.The JDK/conf directory contains ... Read More

JShell is the REPL tool that has introduced in Java 9. We can use this tool to execute simple snippets in the command-line prompt.When we enter an arithmetic expression, variable, etc in JShell, then it displays the result without details of the type of variable created. It is possible in JShell to display more information about the execution of an entered command, use verbose mode. We need to obtain more information on the commands executed by using the command: "/set feedback verbose" (the command can be preceded by "/").In the below snippet, the verbose mode is on, and it can able to ... Read More

JShell is an official Read-Evaluate-Print-Loop (REPL) introduced in Java 9. It provides an interactive shell for quickly prototyping, debugging, and learning Java and Java API without the need for a main() method.The "/list" command in JShell prints out all of the previously typed snippets of that particular session with a unique identifier called the snippet ID. By default, the output doesn't contain any snippet with only valid statements or expressions that can be shown. We need to see all previously typed code include errors, then pass the -all argument to the /list command.In the below code snippet, we have created ... Read More