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JShell in Java 9?
JShell is a new concept introduced in Java 9 version. It provides Java with REPL (Read-Eval-Print-Loop) ability. By using JShell, we can test the java-based logic and expressions without compiling it. REPL acts as an immediate feedback loop and has a great effect on productivity in that particular language.
Step 1: Open Command Prompt and type JShell.
Microsoft Windows [Version 6.3.9600] (c) 2013 Microsoft Corporation. All rights reserved. C:\Users\User>JShell | Welcome to JShell -- Version 9.0.4 | For an introduction type: /help intro jshell>
Step 2: Type /help (to view JShell commands) in the JShell command window once it starts running.
jshell> /help | Type a Java language expression, statement, or declaration. | Or type one of the following commands: | /list [|-all|-start] | list the source you have typed | /edit | edit a source entry referenced by name or id | /drop | delete a source entry referenced by name or id | /save [-all|-history|-start] | Save snippet source to a file. | /open | open a file as source input | /vars [|-all|-start] | list the declared variables and their values | /methods [|-all|-start] | list the declared methods and their signatures | /types [|-all|-start] | list the declared types | /imports | list the imported items | /exit | exit jshell | /env [-class-path ] [-module-path ] [-add-modules < | view or change the evaluation context | /reset [-class-path ] [-module-path ] [-add-modules | reset jshell | /reload [-restore] [-quiet] [-class-path ] [-module-path | reset and replay relevant history -- current or previous ( | /history | history of what you have typed | /help [|] | get information about jshell | /set editor|start|feedback|mode|prompt|truncation|format ... | set jshell configuration information | /? [|] | get information about jshell | /! | re-run last snippet | / | re-run snippet by id | /- | re-run n-th previous snippet | | For more information type '/help' followed by the name of a | command or a subject. | For example '/help /list' or '/help intro'. | | Subjects: | | intro | an introduction to the jshell tool | shortcuts | a description of keystrokes for snippet and command comple | information access, and automatic code generation | context | the evaluation context options for /env /reload and /reset
Step 3: Type /imports in the JShell command window for obtaining the packages imported by JShell.
jshell> /imports | import java.io.* | import java.math.* | import java.net.* | import java.nio.file.* | import java.util.* | import java.util.concurrent.* | import java.util.function.* | import java.util.prefs.* | import java.util.regex.* | import java.util.stream.*
Step 4: Performing calculations in JShell (Try arithmetic calculations with JShell)
jshell> 3+5 $1 ==> 8 jshell> 8-4 $2 ==> 4 jshell> 2*6 $3 ==> 12 jshell> 9%3 $4 ==> 0 jshell> 8/2 $5 ==> 4
Step 5: To exit JShell, type /exit.
jshell> /exit | Goodbye
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