如何在Java 9中获取JShell文档？

Java 9 引入了一种新的交互式工具，称为JShell。该工具可用于执行表达式、类、接口、枚举等。

详细的文档可以在 JShell 中找到，其中包含完整信息，以及使用其内部命令和各种选项的信息。可以使用两个命令访问此文档：“/help”和“/?”。 JShell的文档不仅限于其内部控制的信息，还包括Javadoc。

在下面的代码片段中，可以通过使用“ /help”命令。

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 (-restore) | /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 completion, | information access, and automatic code generation | context | the evaluation context options for /env /reload and /reset登录后复制

JShell 打印不同的现有内部命令，并快速介绍它们的用途，并访问其使用的更详细说明。为此，我们只需输入命令：“/help”，然后输入详细的命令名称（例如“/set”命令）。

jshell> /help /set | | /set | | Set jshell configuration information, including: | the external editor to use, the start-up definitions to use, a new feedback mode, | the command prompt, the feedback mode to use, or the format of output. | | /set editor [-wait] ... | Specify the command to launch for the /edit command. | The is an operating system dependent string. | | /set start | The contents of the specified become the default start-up snippet s and commands. | | /set feedback | Set the feedback mode describing displayed feedback for entered snippets and commands. | | /set mode [] -command|-quiet|-delete | Create or update a user-defined feedback mode, optionally copying from an existing mode. | | /set prompt "" "" | Set the displayed prompts for a given feedback mode. | | /set truncation ... | Set the maximum length of a displayed value. | | /set format "" ... | Configure a feedback mode by setting the format of a field when the selector matches. | | /set | Show editor, start, and feedback settings as /set commands. | To show the settings of any of the above, omit the set value. | | To get more information about one of these forms, use /help with the form specified. | For example: /help /set format登录后复制

我们需要找到第三部分输入的命令，是否修改JShell的返回（/set Feedback），以修改默认编辑器（/set editor），或者修改JShell的启动（/set start）。

jshell> /help /set feedback | Set the feedback mode describing displayed feedback for entered snippets and commands: | | /set feedback [-retain] | | Retain the current feedback mode for future sessions: | | /set feedback -retain | | Show the feedback mode and list available modes: | | /set feedback | | Where is the name of a previously defined feedback mode. | You may use just enough letters to make it unique. | User-defined modes can be added, see '/help /set mode' | | When the -retain option is used, the setting will be used in this and future | runs of the jshell tool. | | The form without or -retain displays the current feedback mode and available modes.登录后复制