在JDK9之后，Java提供了命令行交互工具，就和Python的命令行非常类似，如果配置好Java环境变量，则在命令行z接输入jshell即可进入该交互模式
davieyang@bogon JavaTrainning % jshell
| Welcome to JShell -- Version 11.0.5
| For an introduction type: /help intro
输入/help即可得到命令行工具的各种命令即描述
jshell> /help
| Type a Java language expression, statement, or declaration.
| Or type one of the following commands:
| /list [<name or id>|-all|-start]
| list the source you have typed
| /edit <name or id>
| edit a source entry
| /drop <name or id>
| delete a source entry
| /save [-all|-history|-start] <file>
| Save snippet source to a file
| /open <file>
| open a file as source input
| /vars [<name or id>|-all|-start]
| list the declared variables and their values
| /methods [<name or id>|-all|-start]
| list the declared methods and their signatures
| /types [<name or id>|-all|-start]
| list the type declarations
| /imports
| list the imported items
| /exit [<integer-expression-snippet>]
| exit the jshell tool
| /env [-class-path <path>] [-module-path <path>] [-add-modules <modules>] ...
| view or change the evaluation context
| /reset [-class-path <path>] [-module-path <path>] [-add-modules <modules>]...
| reset the jshell tool
| /reload [-restore] [-quiet] [-class-path <path>] [-module-path <path>]...
| reset and replay relevant history -- current or previous (-restore)
| /history [-all]
| history of what you have typed
| /help [<command>|<subject>]
| get information about using the jshell tool
| /set editor|start|feedback|mode|prompt|truncation|format ...
| set configuration information
| /? [<command>|<subject>]
| get information about using the jshell tool
| /!
| rerun last snippet -- see /help rerun
| /<id>
| rerun snippets by ID or ID range -- see /help rerun
| /-<n>
| rerun n-th previous snippet -- see /help rerun
|
| 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
| id
| a description of snippet IDs and how use them
| shortcuts
| a description of keystrokes for snippet and command completion,
| information access, and automatic code generation
| context
| a description of the evaluation context options for /env /reload and /reset
| rerun
| a description of ways to re-evaluate previously entered snippets
