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Articles by raja
Page 26 of 38
When to use the ServiceLoader class in a module in Java 9?
Java has a ServiceLoader class from java.util package that can help to locate service providers at the runtime by searching in the classpath. For service providers defined in modules, we can look at the sample application to declare modules with service and how it works.For instance, we have a "test.app" module that we need to use Logger that can be retrieved from System.getLogger() factory method with the help of LoggerFinder service.module com.tutorialspoint.test.app { requires java.logging; exports com.tutorialspoint.platformlogging.app; uses java.lang.System.LoggerFinder; }Below is the test.app.MainApp class:package com.tutorialspoint.platformlogging.app; public class MainApp { ...
Read MoreHow to display different list commands in JShell in Java 9?
JShell has introduced in Java 9 and is a command-line tool that allows us to enter simple statements, expressions, methods, and classes without a main () method.When we can enter code in JShell, the code has assigned a unique ID. This ID starts at 1 and has incremented for each command entered in JShell. The same can be true for libraries loaded at startup. For each of these imports, a unique ID has been assigned. It starts with $1 and is incremented for each code loaded ($2, $3 and etc). There is an internal command to list all code loaded, and ...
Read MoreHow to save the current JShell session in Java 9?
Java 9 has introduced a new feature is the creation of a REPL (Read-Evaluate-Print-Loop) called JShell. It is a command-line prompt tool to evaluate Java code without the need to write a complete program.When we can enter code or internal commands in JShell, we need to use it during the current session. When we can close JShell and log-in again, all of the code previously entered has lost. An internal command has been implemented in order to save all code entered into a file using the "/save" command./ save [file-path] / save -all [file-path] / save -history [file-path] / save ...
Read MoreWhat is an unnamed module in Java 9?
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 ...
Read MoreHow to traverse a process tree of Process API in Java 9?
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 ...
Read MoreHow can we get an ID of the running process in Java 9?
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 ...
Read MoreHow can we load a source code into JShell in Java 9?
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 ...
Read MoreWhat are automatic modules in Java 9?
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, ...
Read MoreHow to reset the JShell session in Java 9?
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 MoreWhat are the different feedback modes in JShell in Java 9?
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 ...
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