JSHELL(1)

📦 version 25.0.5.0.3.u1, in arch rolling

💻 JSHELL(1) 💻

okay so this page is literally from the JDK Commands saga bestie, and it's all about jshell — the one that lets you just talk to Java in real time 🫶

✨ NAME ✨

jshell — interactively evaluate declarations, statements, and expressions of the Java programming language in a read-eval-print loop (REPL) 🌸

✨ SYNOPSIS ✨

jshell [options] [load-files]
  • options — command-line options, separated by spaces. See Options for jshell 👀
  • load-files — one or more scripts to run when the tool is started. Scripts can contain any valid code snippets or JShell commands. The script can be a local file or one of following predefined scripts:
    • DEFAULT — loads the default entries, which are commonly used as imports.
    • JAVASE — imports all Java SE packages.
    • PRINTING — defines print, println, and printf as jshell methods for use within the tool.
    • TOOLING — defines javac, jar, and other methods for running JDK tools via their command-line interface within the jshell tool.

For more than one script, use a space to separate the names. Scripts are run in the order in which they're entered on the command line. Command-line scripts are run after startup scripts. To run a script after JShell is started, use the /open command. To accept input from standard input and suppress the interactive I/O, enter a hyphen (-) for load-files. This option enables the use of the jshell tool in pipe chains 🦋

ngl the pipe-chain thing is lowkey iconic, you can absolutely chain jshell into your little shell pipelines 💅

✨ DESCRIPTION ✨

JShell provides a way to interactively evaluate declarations, statements, and expressions of the Java programming language, making it easier to learn the language, explore unfamiliar code and APIs, and prototype complex code. Java statements, variable definitions, method definitions, class definitions, import statements, and expressions are accepted. The bits of code entered are called snippets ✨

As snippets are entered, they're evaluated, and feedback is provided. Feedback varies from the results and explanations of actions to nothing, depending on the snippet entered and the feedback mode chosen. Errors are described regardless of the feedback mode — so you literally can never escape the errors, they will find you 😭. Start with the verbose mode to get the most feedback while learning the tool. Bestie, trust, verbose first.

Command-line options are available for configuring the initial environment when JShell is started. Within JShell, commands are available for modifying the environment as needed 🎀

Existing snippets can be loaded from a file to initialize a JShell session, or at any time within a session. Snippets can be modified within the session to try out different variations and make corrections. To keep snippets for later use, save them to a file. Obsessed with the save-your-work energy, fr fr 💖

✨ OPTIONS FOR JSHELL ✨

okay this is the big one, buckle up 🎢

  • --add-exports module/package — specifies a package to be considered as exported from its defining module.
  • --add-modules module[,module...] — specifies the root modules to resolve in addition to the initial module.
  • -Cflag — passes flag to the Java compiler inside JShell. For example, -C-Xlint enables all the recommended lint warnings, and -C--release=<N> compiles for Java SE N, as if --release N was specified. 🛠️
  • --class-path path — specifies the directories and archives that are searched to locate class files. This option overrides the path in the CLASSPATH environment variable. If the environment variable isn't set and this option isn't used, then the current directory is searched. For Linux and macOS, use a colon (:) to separate items in the path. For Windows, use a semicolon (;) to separate items. 🗂️
  • --enable-preview — allows code to depend on the preview features of this release. (preview = spicy unstable vibes, handle with care 💀)
  • --execution specification — specifies an alternate execution engine, where specification is an ExecutionControl spec. See the documentation of the package jdk.jshell.spi for the syntax of the spec.
  • --feedback mode — sets the initial level of feedback provided in response to what's entered. The initial level can be overridden within a session by using the /set feedback mode command. The default is normal. The following values are valid for mode:
    • verbose — provides detailed feedback for entries. Additional information about the action performed is displayed after the result of the action. The next prompt is separated from the feedback by a blank line.
    • normal — provides an average amount of feedback. The next prompt is separated from the feedback by a blank line.
    • concise — provides minimal feedback. The next prompt immediately follows the code snippet or feedback.
    • silent — provides no feedback. The next prompt immediately follows the code snippet. 🤫
    • custom — provides custom feedback based on how the mode is defined. Custom feedback modes are created within JShell by using the /set mode command.
  • --help or -h or -? — prints a summary of standard options and exits the tool.
  • --help-extra or -X — prints a summary of nonstandard options and exits the tool. Nonstandard options are subject to change without notice ⚠️
  • -Jflag — passes flag to the runtime system, but has no effect on the execution of code snippets. To specify flags that affect the execution of code snippets, use -Rflag. Alternatively, use -Jflag with --execution local. 🧚
  • --module-path modulepath — specifies where to find application modules. For Linux and macOS, use a colon (:) to separate items in the path. For Windows, use a semicolon (;) to separate items.
  • --no-startup — prevents startup scripts from running when JShell starts. Use this option to run only the scripts entered on the command line when JShell is started, or to start JShell without any preloaded information if no scripts are entered. This option can't be used if the --startup option is used. 🚫
  • -q — sets the feedback mode to concise, which is the same as entering --feedback concise.
  • -Rflag — passes flag to the runtime system only when code snippets are executed. For example, -R-Dfoo=bar means that execution of the snippet System.getProperty("foo") will return "bar". 🔥
  • -s — sets the feedback mode to silent, which is the same as entering --feedback silent.
  • --show-version — prints version information and enters the tool.
  • --startup file — overrides the default startup script for this session. The script can contain any valid code snippets or commands. The script can be a local file or one of the following predefined scripts:
    • DEFAULT — loads the default entries, which are commonly used as imports.
    • JAVASE — imports all Java SE packages.
    • PRINTING — defines print, println, and printf as jshell methods for use within the tool.
    • TOOLING — defines javac, jar, and other methods for running JDK tools via their command-line interface within the jshell tool.

For more than one script, provide a separate instance of this option for each script. Startup scripts are run when JShell is first started and when the session is restarted with the /reset, /reload, or /env command. Startup scripts are run in the order in which they're entered on the command line. This option can't be used if the --no-startup option is used. 🌈

  • -v — sets the feedback mode to verbose, which is the same as entering --feedback verbose.
  • --version — prints version information and exits the tool.

✨ JSHELL COMMANDS ✨

Within the jshell tool, commands are used to modify the environment and manage code snippets 🎀 these are the slash-commands, iykyk.

  • /drop {name|id|startID-endID} [{name|id|startID-endID}...] — drops snippets identified by name, ID, or ID range, making them inactive. For a range of IDs, provide the starting ID and ending ID separated with a hyphen. To provide a list, separate the items in the list with a space. Use the /list command to see the IDs of code snippets. 💅
  • /edit [option] — opens an editor. If no option is entered, then the editor opens with the active snippets. The following options are valid:
    • {name|id|startID-endID} [{name|id|startID-endID}...] — opens the editor with the snippets identified by name, ID, or ID range. For a range of IDs, provide the starting ID and ending ID separated with a hyphen. To provide a list, separate the items in the list with a space. Use the /list command to see the IDs of code snippets.
    • -all — opens the editor with all snippets, including startup snippets and snippets that failed, were overwritten, or were dropped. 👑
    • -start — opens the editor with startup snippets that were evaluated when JShell was started. To exit edit mode, close the editor window, or respond to the prompt provided if the -wait option was used when the editor was set. Use the /set editor command to specify the editor to use. If no editor is set, then the following environment variables are checked in order: JSHELLEDITOR, VISUAL, and EDITOR. If no editor is set in JShell and none of the editor environment variables is set, then a simple default editor is used. 🦋
  • /env [options] — displays the environment settings, or updates the environment settings and restarts the session. If no option is entered, then the current environment settings are displayed. If one or more options are entered, then the session is restarted as follows:
    1. Updates the environment settings with the provided options.
    2. Resets the execution state.
    3. Runs the startup scripts.
  • Silently replays the history in the order entered. The history includes all valid snippets or /drop commands entered at the jshell prompt, in scripts entered on the command line, or scripts entered with the /open command. Environment settings entered on the command line or provided with a previous /reset, /env, or /reload command are maintained unless an option is entered that overwrites the setting. The following options are valid:
    • --add-modules module[,module...] — Specifies the root modules to resolve in addition to the initial module.
    • --add-exports source-module/package=target-module[,target-module]* — Adds an export of package from source-module to target-module.
    • --class-path path — Specifies the directories and archives that are searched to locate class files. This option overrides the path in the CLASSPATH environment variable. If the environment variable isn't set and this option isn't used, then the current directory is searched. For Linux and macOS, use a colon (:) to separate items in the path. For Windows, use a semicolon (;) to separate items.
    • --module-path modulepath — Specifies where to find application modules. For Linux and macOS, use a colon (:) to separate items in the path. For Windows, use a semicolon (;) to separate items.

🚪 The rest of the / commands, bestie

  • /exit [integer-expression-snippet] — Exits the tool. If no snippet is entered, the exit status is zero. If a snippet is entered and the result of the snippet is an integer, the result is used as the exit status. If an error occurs, or the result of the snippet is not an integer, an error is displayed and the tool remains active. (so like… it refuses to let you leave dramatically. iconic of it, honestly.)
  • /history — Displays what was entered in this session.
  • /help [command|subject] — Displays information about commands and subjects. If no options are entered, then a summary of information for all commands and a list of available subjects are displayed. If a valid command is provided, then expanded information for that command is displayed. If a valid subject is entered, then information about that subject is displayed.

The following values for subject are valid:

  • context — Describes the options that are available for configuring the environment.
  • intro — Provides an introduction to the tool.
  • shortcuts — Describes keystrokes for completing commands and snippets. See Input Shortcuts.
  • /imports — Displays the current active imports, including those from the startup scripts and scripts that were entered on the command line when JShell was started. (peep the receipts ✨)
  • /list [option] — Displays a list of snippets and their IDs. If no option is entered, then all active snippets are displayed, but startup snippets aren't.

The following options are valid:

  • {name|id|startID-endID} [{name|id|startID-endID}...] — Displays the snippets identified by name, ID, or ID range. For a range of IDs, provide the starting ID and ending ID separated with a hyphen. To provide a list, separate the items in the list with a space.
  • -all — Displays all snippets, including startup snippets and snippets that failed, were overwritten, or were dropped. IDs that begin with s are startup snippets. IDs that begin with e are snippets that failed. (the whole group chat, even the deleted messages fr)
  • -start — Displays startup snippets that were evaluated when JShell was started.
  • /methods [option] — Displays information about the methods that were entered. If no option is entered, then the name, parameter types, and return type of all active methods are displayed.

The following options are valid:

  • {name|id|startID-endID} [{name|id|startID-endID}...] — Displays information for methods identified by name, ID, or ID range. For a range of IDs, provide the starting ID and ending ID separated with a hyphen. To provide a list, separate the items in the list with a space. Use the /list command to see the IDs of code snippets.
  • -all — Displays information for all methods, including those added when JShell was started, and methods that failed, were overwritten, or were dropped.
  • -start — Displays information for startup methods that were added when JShell was started.
  • /open file — Opens the script specified and reads the snippets into the tool. The script can be a local file or one of the following predefined scripts:
    • DEFAULT — Loads the default entries, which are commonly used as imports.
    • JAVASE — Imports all Java SE packages.
    • PRINTING — Defines print, println, and printf as jshell methods for use within the tool.
    • TOOLING — Defines javac, jar, and other methods for running JDK tools via their command-line interface within the jshell tool.
  • /reload [options] — Restarts the session as follows:
    • Updates the environment settings with the provided options, if any.
    • Resets the execution state.
    • Runs the startup scripts.
    • Replays the history in the order entered. The history includes all valid snippets or /drop commands entered at the jshell prompt, in scripts entered on the command line, or scripts entered with the /open command. Environment settings entered on the command line or provided with a previous /reset, /env, or /reload command are maintained unless an option is entered that overwrites the setting. The following options are valid:
      • --add-modules module[,module...] — Specifies the root modules to resolve in addition to the initial module.
      • --add-exports source-module/package=target-module[,target-module]* — Adds an export of package from source-module to target-module.
      • --class-path path — Specifies the directories and archives that are searched to locate class files. This option overrides the path in the CLASSPATH environment variable. If the environment variable isn't set and this option isn't used, then the current directory is searched. For Linux and macOS, use a colon (:) to separate items in the path. For Windows, use a semicolon (;) to separate items.
      • --module-path modulepath — Specifies where to find application modules. For Linux and macOS, use a colon (:) to separate items in the path. For Windows, use a semicolon (;) to separate items.
      • -quiet — Replays the valid history without displaying it. Errors are displayed. (stealth mode, but the drama still shows up 💀)
      • -restore — Resets the environment to the state at the start of the previous run of the tool or to the last time a /reset, /reload, or /env command was executed in the previous run. The valid history since that point is replayed. Use this option to restore a previous JShell session. (time machine behaviour, no cap)
  • /reset [options] — Discards all entered snippets and restarts the session as follows:
    • Updates the environment settings with the provided options, if any.
    • Resets the execution state.
    • Runs the startup scripts. History is not replayed. All code that was entered is lost. Environment settings entered on the command line or provided with a previous /reset, /env, or /reload command are maintained unless an option is entered that overwrites the setting. The following options are valid:
      • --add-modules module[,module...] — Specifies the root modules to resolve in addition to the initial module.
      • --add-exports source-module/package=target-module[,target-module]* — Adds an export of package from source-module to target-module.
      • --class-path path — Specifies the directories and archives that are searched to locate class files. This option overrides the path in the CLASSPATH environment variable. If the environment variable isn't set and this option isn't used, then the current directory is searched. For Linux and macOS, use a colon (:) to separate items in the path. For Windows, use a semicolon (;) to separate items.
      • --module-path modulepath — Specifies where to find application modules. For Linux and macOS, use a colon (:) to separate items in the path. For Windows, use a semicolon (;) to separate items.
Heads up bestie: this one does not replay history. Your code is gone gone. 🫶
  • /save [options] file — Saves snippets and commands to the file specified. If no options are entered, then active snippets are saved.

The following options are valid:

  • {name|id|startID-endID} [{name|id|startID-endID}...] — Saves the snippets and commands identified by name, ID, or ID range. For a range of IDs, provide the starting ID and ending ID separated with a hyphen. To provide a list, separate the items in the list with a space. Use the /list command to see the IDs of the code snippets.
  • -all — Saves all snippets, including startup snippets and snippets that were overwritten or failed.
  • -history — Saves the sequential history of all commands and snippets entered in the current session.
  • -start — Saves the current startup settings. If no startup scripts were provided, then an empty file is saved.
  • /set [setting] — Sets configuration information, including the external editor, startup settings, and feedback mode. This command is also used to create a custom feedback mode with customized prompt, format, and truncation values. If no setting is entered, then the current setting for the editor, startup settings, and feedback mode are displayed.

The following values are valid for setting:

editor [options] [command] : this one sets the external editor that pops open when you type /edit 💅. The command can totally include arguments — just separate them with spaces. Type it with no command and no options and it'll show you the current setting, no cap.

The options that are valid:

  • -default — points your editor at the default editor that ships with JShell. You can't use this one if you're also entering a command for starting an editor (pick a lane bestie).
  • -delete — sets the editor back to whatever was in effect when the session started. But ooh, if you use it with -retain, then the retained editor setting gets deleted and the editor gets set to the first of these environment variables that it finds: JSHELLEDITOR, VISUAL, or EDITOR. And if none of those editor env vars are set? It just sets the default editor. Also can't be used if you're entering a command for starting an editor.
  • -retain — saves your editor setting across sessions, so it survives ✨. If you enter no other option and no command, then the current setting is what gets saved.
  • -wait — makes it prompt you to say when editing is done. Otherwise control just goes back to JShell the moment the editor exits. Use this one if your editor exits immediately, like when an edit window already exists. This option is valid only when a command for starting an editor is entered.

feedback [mode] : sets the feedback mode JShell uses to respond to your input. No mode entered? It shows you the current mode 🫶.

The modes that are valid: concise, normal, silent, verbose, and any custom mode you made with the /set mode command.

format mode field "format-string" selector : sets the format of the feedback you get back. And listen, the display rules here are a whole ladder:

  • No mode entered → it shows the current formats for all fields for all feedback modes.
  • Only a mode entered → it shows the current formats for that mode.
  • Only a mode and field entered → it shows the current formats for that field.

To actually define a format, these arguments are required:

  • mode — the feedback mode the response format applies to. Heads up: only custom modes created with the /set mode command can be modified.
  • field — the context-specific field the response format applies to. The fields are described in the online help, which you get to from JShell with the /help /set format command.
  • "format-string" — the string to use as the response format for that field and selector. The structure of the format string is also described in the online help, accessed from JShell using /help /set format.
  • selector — the context in which the response format is applied. Selectors are described in the online help too — /help /set format from inside JShell, iykyk.

mode [mode-name] [existing-mode] [options] : makes a custom feedback mode with the name you give it 🎀. If you enter no mode name, it displays the settings for all modes — that includes the mode, prompt, format, and truncation settings. If you hand it the name of an existing mode, the settings from that existing mode get copied over to the new one you're creating. Slay.

The options that are valid:

  • -command | -quiet — sets the level of feedback shown for commands when you're using the mode. This option is required when creating a feedback mode. Use -command to show information and verification feedback for commands. Use -quiet to show only the essential feedback for commands, like error messages.
  • -delete — deletes the named feedback mode for this session. The name of the mode to delete is required. Want it gone permanently? Use -retain together with this option if the mode was retained. Predefined modes can't be deleted, sorry bestie 💀.
  • -retain — saves the named feedback mode across sessions. The name of the mode to retain is required. Configure your new feedback mode using the /set prompt, /set format, and /set truncation commands. And to start using the new mode, use the /set feedback command 👑

prompt mode "prompt-string" "continuation-prompt-string" : sets the prompts for input inside JShell 🌸.

  • No mode entered → it shows the current prompts for all feedback modes.
  • Only a mode entered → it shows the current prompts for that mode.

To define a prompt, these arguments are required:

  • mode — the feedback mode the prompts apply to. Only custom modes created with the /set mode command can be modified.
  • "prompt-string" — the string to use as the prompt for the first line of input.
  • "continuation-prompt-string" — the string to use as the prompt for the extra input lines needed to complete a snippet.

start [-retain] [file [file...]|option] : sets the names of the startup scripts used the next time you type /reset, /reload, or /env. Enter more than one script and they run in the order you entered them 🦋. No scripts and no options? It shows the current startup settings.

Your scripts can be local files, or one of these predefined scripts:

  • DEFAULT — loads the default entries, which are commonly used as imports.
  • JAVASE — imports all Java SE packages.
  • PRINTING — defines print, println, and printf as jshell methods for use inside the tool.
  • TOOLING — defines javac, jar, and other methods for running JDK tools via their command-line interface inside the jshell tool.

And the options that are valid:

  • -default — sets the startup settings back to the default settings.
  • -none — specifies that no startup settings are used. Use the -retain option to save the start setting across sessions.

truncation mode length selector : sets the max length of a displayed value ✂️. No mode entered → it shows the current truncation values for all feedback modes. Only a mode entered → it shows the current truncation values for that mode.

To define truncation values, these arguments are required:

  • mode — the feedback mode the truncation value applies to. Only custom modes created with the /set mode command can be modified.
  • length — the unsigned integer to use as the maximum length for the specified selector.
  • selector — the context in which the truncation value applies. Selectors are described in the online help, which you access from JShell with the /help /set truncation command.

💜 /types [option]

Displays the classes, interfaces, and enums you entered. If you enter no option, then all the current active classes, interfaces, and enums get displayed 🌈.

The options that are valid:

  • {name|id|startID-endID} [{name|id|startID-endID}...] — displays info for the classes, interfaces, and enums identified by name, ID, or ID range. For a range of IDs, give the starting ID and ending ID separated with a hyphen. For a list, separate the items with a space. Use the /list command to see the IDs of the code snippets 👀.
  • -all — displays info for all classes, interfaces, and enums, including the ones added when JShell was started, plus the ones that failed, were overwritten, or were dropped. Everyone's invited to this party 💀.
  • -start — displays info for startup classes, interfaces, and enums that were added when JShell was started.

🍓 /vars [option]

Displays the name, type, and value of the variables you entered. No option entered? All the current active variables show up 💖.

The options that are valid:

  • {name|id|startID-endID} [{name|id|startID-endID}...] — displays info for variables identified by name, ID, or ID range. For a range of IDs, give the starting ID and ending ID separated with a hyphen. For a list, separate the items with a space. Use the /list command to see the IDs of the code snippets ✨.
  • -all — Displays information for all variables, including those added when JShell was started, and variables that failed, were overwritten, or were dropped.
  • -start — Displays information for startup variables that were added when JShell was started.
  • /? — Same as the /help command.
  • /! — Reruns the last snippet.
  • /{name|id|startID-endID} [{name|id|startID-endID}...] — Reruns the snippets identified by ID, range of IDs, or name. For a range of IDs, provide the starting ID and ending ID separated with a hyphen. To provide a list, separate the items in the list with a space. The first item in the list must be an ID or ID range. Use the /list command to see the IDs of the code snippets.
  • /-n — Reruns the -nth previous snippet. For example, if 15 code snippets were entered, then /-4 runs the 11th snippet. Commands aren't included in the count.

✨ INPUT SHORTCUTS ✨

The following shortcuts are available for entering commands and snippets in JShell. 💅

🎀 Tab completion 🎀

  • <tab> — When entering snippets, commands, subcommands, command arguments, or command options, use the Tab key to automatically complete the item. If the item can't be determined from what was entered, then possible options are provided.

When entering a method call, use the Tab key after the method call's opening parenthesis to see the parameters for the method. If the method has more than one signature, then all signatures are displayed. Pressing the Tab key a second time displays the description of the method and the parameters for the first signature. Continue pressing the Tab key for a description of any additional signatures. 🫶

  • Shift+<Tab> V — After entering a complete expression, use this key sequence to convert the expression to a variable declaration of a type determined by the type of the expression.
  • Shift+<Tab> M — After entering a complete expression or statement, use this key sequence to convert the expression or statement to a method declaration. If an expression is entered, the return type is based on the type of the expression.
  • Shift+<Tab> I — When an identifier is entered that can't be resolved, use this key sequence to show possible imports that resolve the identifier based on the content of the specified class path.

🎀 Command abbreviations 🎀

An abbreviation of a command is accepted if the abbreviation uniquely identifies a command. For example, /l is recognized as the /list command. However, /s isn't a valid abbreviation because it can't be determined if the /set or /save command is meant. Use /se for the /set command or /sa for the /save command. ✨

Abbreviations are also accepted for subcommands, command arguments, and command options. For example, use /m -a to display all methods.

🎀 History navigation 🎀

A history of what was entered is maintained across sessions. Use the up and down arrows to scroll through commands and snippets from the current and past sessions. Use the Ctrl key with the up and down arrows to skip all but the first line of multiline snippets. 🌸

Use the Ctrl+R key combination to search the history for the string entered. The prompt changes to show the string and the match. Ctrl+R searches backwards from the current location in the history through earlier entries. Ctrl+S searches forward from the current location in the history though later entries. 🔥

💜 INPUT EDITING 💜

The editing capabilities of JShell are similar to that of other common shells. Keyboard keys and key combinations provide line editing shortcuts. The Ctrl key and Meta key are used in key combinations. If your keyboard doesn't have a Meta key, then the Alt key is often mapped to provide Meta key functionality. 💅

🦋 Line Editing Shortcuts 🦋

  • Return — Enter the current line.
  • Left arrow — Move the cursor to the left one character.
  • Right arrow — Move the cursor to the right one character.
  • Ctrl+A — Move the cursor to the beginning of the line.
  • Ctrl+E — Move the cursor to the end of the line.
  • Meta+B — Move the cursor to the left one word.
  • Meta+F — Move the cursor to the right one word.
  • Delete — Delete the character under the cursor.
  • Backspace — Delete the character before the cursor.
  • Ctrl+K — Delete the text from the cursor to the end of the line.
  • Meta+D — Delete the text from the cursor to the end of the word.
  • Ctrl+W — Delete the text from the cursor to the previous white space.
  • Ctrl+Y — Paste the most recently deleted text into the line.
  • Meta+Y — After Ctrl+Y, press to cycle through the previously deleted text.

🌈 EXAMPLE OF STARTING AND STOPPING A JSHELL SESSION 🌈

JShell is provided with the JDK. To start a session, enter jshell on the command line. A welcome message is printed, and a prompt for entering commands and snippets is provided. 🎀

% jshell
|  Welcome to JShell -- Version 9
|  For an introduction type: /help intro

jshell>

To see which snippets were automatically loaded when JShell started, use the /list -start command. The default startup snippets are import statements for common packages. The ID for each snippet begins with the letter s, which indicates it's a startup snippet. ✨

jshell> /list -start

  s1 : import java.io.*;
  s2 : import java.math.*;
  s3 : import java.net.*;
  s4 : import java.nio.file.*;
  s5 : import java.util.*;
  s6 : import java.util.concurrent.*;
  s7 : import java.util.function.*;
  s8 : import java.util.prefs.*;
  s9 : import java.util.regex.*;
 s10 : import java.util.stream.*;

jshell>

To end the session, use the /exit command. 👋

jshell> /exit
|  Goodbye

%

🍓 EXAMPLE OF ENTERING SNIPPETS 🍓

Snippets are Java statements, variable definitions, method definitions, class definitions, import statements, and expressions. Terminating semicolons are automatically added to the end of a completed snippet if they're missing. 💖

The following example shows two variables and a method being defined, and the method being run. Note that a scratch variable is automatically created to hold the result because no variable was provided. 🫶

jshell> int a=4
a ==> 4

jshell> int b=8
b ==> 8

jshell> int square(int i1) {
   ...> return i1 * i1;
   ...> }
|  created method square(int)

jshell> square(b)
$5 ==> 64

🧚 EXAMPLE OF CHANGING SNIPPETS 🧚

Change the definition of a variable, method, or class by entering it again. ✨

The following examples shows a method being defined and the method run:

jshell> String grade(int testScore) {
   ...>     if (testScore >= 90) {
   ...>         return "Pass";
   ...>     }
   ...>     return "Fail";
   ...> }
|  created method grade(int)

jshell> grade(88)
$3 ==> "Fail"

To change the method grade to allow more students to pass, enter the method definition again and change the pass score to 80. Use the up arrow key to retrieve the previous entries to avoid having to reenter them and make the change in the if statement. The following example shows the new definition and reruns the method to show the new result: 💅

jshell> String grade(int testScore) {
   ...>     if (testScore >= 80) {
   ...>         return "Pass";
   ...>     }
   ...>     return "Fail";
   ...> }
|  modified method grade(int)

jshell> grade(88)
$5 ==> "Pass"

For snippets that are more than a few lines long, or to make more than a few changes, use the /edit command to open the snippet in an editor. After the changes are complete, close the edit window to return control to the JShell session. The following example shows the command and the feedback provided when the edit window is closed. The /list command is used to show that the pass score was changed to 85. 👑

jshell> /edit grade
|  modified method grade(int)
jshell> /list grade

   6 : String grade(int testScore) {
           if (testScore >= 85) {
               return "Pass";
           }
           return "Fail";
       }

✨ EXAMPLE OF CREATING A CUSTOM FEEDBACK MODE ✨

ok so bestie, real talk — the feedback mode is literally the whole vibe of your jshell session 💅 it decides three things: the prompt you see, the little feedback messages that pop up when you enter snippets, and the max length of a displayed value. And guess what? There are predefined feedback modes already, plus commands so you can build your own. obsessed.

Use the /set mode command to create a new feedback mode. In the example below, the brand new mode mymode is based on the predefined feedback mode normal, and -command makes sure the command feedback is displayed:

jshell> /set mode mymode normal -command
|  Created new feedback mode: mymode

Since the new mode is based on normal, the prompts are the same. The next example shows how to peek at what prompts are in use, and then how to switch them over to custom strings. Heads up: the first string is the standard JShell prompt, and the second string is the prompt for extra lines in multiline snippets:

jshell> /set prompt mymode
|  /set prompt mymode "\njshell> " "   ...> "

jshell> /set prompt mymode "\nprompt$ " "   continue$ "

The maximum length of a displayed value? That's controlled by the truncation setting, and different types of values can have different lengths 🎀 The following example sets an overall truncation value of 72, plus a truncation value of 500 for variable value expressions:

jshell> /set truncation mymode 72

jshell> /set truncation mymode 500 varvalue

Then there's the feedback shown after snippets are entered — that's controlled by the format setting, and it's based on the type of snippet entered plus the action taken for that snippet. In the predefined mode normal, that string gets created when a method is created. Here's how to change that string to defined:

jshell> /set format mymode action "defined" added-primary

Now use the /set feedback command to actually start using the feedback mode you just made. The example below shows the custom mode in action 🔥

jshell> /set feedback mymode
|  Feedback mode: mymode

prompt$ int square (int num1){
   continue$ return num1*num1;
   continue$ }
|  defined method square(int)

prompt$

and that's the whole page, bestie — you made it to the end 🫶 go forth and customize those prompts, no cap. this one's from JDK 25.0.5.0.3, dated 2026, and it ate fr fr 💖✨🎀

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