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Java Articles
Page 334 of 450
What is the purpose of using JLink in Java 9?
The main purpose of the JLink feature is to create our own Customized JRE. Usually, we run a program with the default JRE that has been provided by Oracle Corporation with 214 MB of size.For instance, a user wants to print a simple "Hello World" message as shown belowpublic class HelloWorldModuleTest { public static void main(String args[[]) { System.out.println("Hello World!"); } }To run the above program of 1 KB size, we need 4 – 5 classes like String, System, Object, and HelloWorldModuleTest.class files. Then why do we need to load 214 MB of JRE using ...
Read MoreImportance of Module Descriptor in a Module in Java 9?
A module is a collection of code in the form of classes organized in packages and static resources such as property files or others. It provides the outside environment with all the information that can be required to use that module. The module descriptor is a key source of the module system, and it's compiled version of a module declaration specified in a file named "module-info.java" file at the root of the module’s directory hierarchy.The module describes itself by a module declaration as belowmodule com.myproject.module1 { requires com.myproject.module2; exports com.myproject.project1; exports com.myproject.project2; }Below are some of the module descriptors described:module module. name: declares a module ...
Read MoreWhy @SafeVarargs is required in Java 9?
The varargs functionality has been introduced in Java to facilitate the creation of methods with a variable number of arguments without resorting to array-type parameters or overloaded versions of the same method.Before Java 9 versions, if vararg methods are used with generics, then there is a warning message. Even though not all methods create heap pollution, compiler shows warning for all vararg methods used with generics. That's the reason @SafeVarargs concept was added to Java 9 version to avoid these warnings. If we added this annotation, then the compiler stops these warnings.We can compile the code by using the below ...
Read MoreHow to re-execute existing snippets in JShell in Java 9?
JShell is the first REPL tool introduced in Java 9. We can able to execute simple snippets in a command-line prompt by using JShell tool. We can start a JShell session by typing "jshell" command, stop the session by typing "/exit" command, and search for particular command by using "/help" command.The "/reload" command can be used to re-execute all existing snippets in JShell. We can also remove all prior code from a JShell session by using the "/reset" command.In the below code snippet, we have created a set of snippets.jshell> 2+10 $1 ==> 12 jshell> String s = "Tutorialspoint" ...
Read MoreDifferences between Java 8 and Java 9?
Java 9 version has introduced new enhancements and added new features. It includes JShell, Http2Client, Java Platform Module System (JPMS), Multi-release jar files, Stack Walking API, Private methods in an interface, Process API updates, Collection API updates, Stream API improvements, and etc.Below are the few differences between Java 8 and Java 9In Java 8 and earlier versions, the top-level component is the package. It places a set of related types (classes, interfaces, enums, and etc) into a group, and also contains a set of resources whereas Java 9 introduces a new component: module, which can be used to place a ...
Read MoreHow can we execute snippets by ID in JShell in Java 9?
JShell is an interactive tool (REPL) introduced in Java 9. We can execute snippets like expressions, variables, methods, classes, and etc without a main () method in the JShell tool.We can execute any prior snippet by simply typing /id, which indicates the snippet’s ID. For instance, if we type "/1", then JShell can display the first snippet that we have entered, executes it, and shows the result. We can re-execute the last snippet that we have entered (whether it is valid or invalid) by using "/!".In the below code snippet, we have created a set of snippets, and execute those ...
Read MoreHow can we avoid compilation errors in JShell in Java 9?
JShell is an interactive tool that enables us to execute java code and displays the output instantly. JShell is the REPL(Read-Evaluate-Print-Loop) tool that runs from the command-line prompt. If we need to avoid the compilation-errors in JShell, then we must declare those variables before using it. The error message in JShell can use the notation "^--^" to highlight an error.In the below code snippet, the declaration of an int variable "div" attempts to use variables: num1, and num2 that has not been declared, so JShell reports a compilation error, indicating that the compiler was unable to find those variables.C:\Users\User>jshell | ...
Read MoreWhat are the components in a module-info file in Java 9?
A module is an independent unit of application that represents a single functionality. A module contains three important componentsName: To uniquely identify itDependencies: Other modules in which it depends onExported packages: Packages which are open for external applicationIn order to declare a module, we need to add the "module-info.java" file to the root source code. The components of the "module-info.java" file includes "name", "requires", "exports", and "exports to".Below is the template of "module-info.java" filemodule { requires ; requires ; ... exports ; exports ; ... exports to ; }Name: It is ...
Read MoreHow can we display all module names in Java 9?
In Java 9, the module concept has introduced. It is a named, self-describing collection of code and data. The code can be organized as a set of packages containing types like java classes and interfaces, and data includes resources and other kinds of static information. A module contains a name, dependencies, and exported packages.Syntaxmodule com.tutorialspoint.mymodule { // some statements }In the below example, we can able to display all module names by using the ModuleLayer class.Examplepublic class AllModulesNamesTest { public static void main(String args[]) { ModuleLayer.boot().modules().forEach((module) -> { ...
Read MoreHow to print the pattern of stars in JShell in Java 9?
JShell is a REPL tool introduced in Java 9 that allows us to execute Java code and getting results immediately. We can evaluate expressions or simple algorithms without creating a new project, compile or build it by using JShell. We can also execute expressions, use imports, define classes, methods, and variables. It is a part of Java 9 JDK but not JRE.We can start JShell session in command-prompt by simply typing jshell. We can use different commands: /exit to quit the JShell session, reset/reload JShell anytime by typing /reset, and /reload, /import to list the imports, etc.In the below example, ...
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