java 15: 用jshell体验交互式java编程

一，jshell查看帮助

[lhdop@blog ~]$ jshell --help
Usage:   jshell <option>... <load-file>...
where possible options include:
    --class-path <path>   Specify where to find user class files
    --module-path <path>  Specify where to find application modules
    --add-modules <module>(,<module>)*
…

说明：刘宏缔的架构森林是一个专注架构的博客，

网站：https://blog.imgtouch.com
本文: https://blog.imgtouch.com/index.php/2023/06/01/java-15-yong-jshell-ti-yan-jiao-hu-shi-java-bian-cheng/

         对应的源码可以访问这里获取： https://github.com/liuhongdi/
         或: https://gitee.com/liuhongdi

说明：作者:刘宏缔 邮箱: 371125307@qq.com

二，jshell的使用

1, -v : 详细模式启动JShel

[lhdop@blog ~]$ jshell -v
|  Welcome to JShell -- Version 15
|  For an introduction type: /help intro
jshell>

2,退出:

jshell> /exit
|  Goodbye

3,一个整数相加的例子:

jshell> int x = 35;
x ==> 35
|  created variable x : int
 
jshell> int y = 33;
y ==> 33
|  created variable y : int
 
jshell> int z = x + y;
z ==> 68
|  created variable z : int
 
jshell> System.out.println(z);
68

4,jshell中使用函数

jshell> Math.pow(2,3)
$1 ==> 8.0
|  created scratch variable $1 : double 

5,jshell中使用HashMap

jshell> HashMap<Integer,String> mapOne = new HashMap<Integer,String>();
mapOne ==> {}
|  created variable mapOne : HashMap<Integer, String>
 
jshell> mapOne.put(35,"thirty five");
$3 ==> null
|  created scratch variable $3 : String
 
jshell> mapOne.get(35);
$4 ==> "thirty five"
|  created scratch variable $4 : String

6,jshell中自定义函数

jshell> String glue(String a,String b) {
   ...>     return a+","+b;
   ...> }
|  created method glue(String,String)
 
jshell> glue("laoliu","good")
$6 ==> "laoliu,good"
|  created scratch variable $6 : String

7,jshell中的内置命令:

/vars 查看变量

jshell> /vars
|    double $1 = 8.0
|    HashMap<Integer, String> mapOne = {35=thirty five}
|    String $3 = null
|    String $4 = "thirty five”

/list 列出执行过的代码片段

jshell> /list
   1 : Math.pow(2,3)
   2 : HashMap<Integer,String> mapOne = new HashMap<Integer,String>();
   3 : mapOne.put(35,"thirty five");
   4 : mapOne.get(35);

 /methods 列出自定义的方法

jshell> /methods
| String glue(String,String)

/ 列出所有命令

jshell> /
|  Command: '/' is ambiguous: /list, /edit, /drop, /save, /open, /vars, /methods, /types, /imports, 
   /exit, /env, /reset, /reload, /history, /debug, /help, /set, /?, /!
|  Type /help for help.

/help 详细的帮助

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
...

三，查看java的版本:

[lhdop@blog tools]$ java --version
java 15 2020-09-15
Java(TM) SE Runtime Environment (build 15+36-1562)
Java HotSpot(TM) 64-Bit Server VM (build 15+36-1562, mixed mode, sharing)