Java REPL & JShell
Java 11
JShell
Java Shell
https://www.infoq.com/articles/jshell-java-repl/
The Java Shell or JShell is an official Read-Evaluate-Print-Loop, or REPL as it's commonly called, introduced with Java 9.
It provides an interactive shell for quickly prototyping, debugging, and learning Java and Java APIs, all without the need for a public static void main or the need to compile your code before executing it.
And as an added plus, using JShell just got a whole lot less verbose (and more practical) with the advent of the var keyword in Java 10!
Last login: Sat Aug 1 12:20:36 on ttys006
➜ ~ jshell
| Welcome to JShell -- Version 11.0.2
| For an introduction type: /help intro
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
jshell> /exit
| Goodbye
online REPL
OpenJDK Runtime Environment (build 11.0.6+10-post-Ubuntu-1ubuntu118.04.1)
https://java-repl.xgqfrms.repl.run
https://repl.it/@xgqfrms/java-repl#HelloWorld.java
javac -classpath .:/run_dir/junit-4.12.jar:target/dependency/* -d . HelloWorld.java Main.java
java -classpath .:/run_dir/junit-4.12.jar:target/dependency/* Main
Hello world!
demos
⚠️ 创建文件 HelloWorld.java 的文件名必须要与类名保持一致
// HelloWorld.java
public class HelloWorld {
public static void main(String[] args) {
System.out.println("Hello World");
}
}
注：String args[] 与 String[] args 都可以执行，但推荐使用 String[] args，这样可以避免歧义和误读。
$ javac --version
# javac 11.0.2
$ javac HelloWorld.java
$ java HelloWorld
# Hello World
refs
https://www.runoob.com/java/java-tutorial.html
©xgqfrms 2012-2020
www.cnblogs.com 发布文章使用：只允许注册用户才可以访问！