运行来自 Jshell 的回显示例

Question

我看过这样一个命令行参数的例子：

public class Echo {
    public static void main (String[] args) {
        for (String s: args) {
            System.out.println(s);
        }
    }
}

它运行从命令行正确，我怎么能从 Jshell 运行它？

jshell> Echo.main testing
|  created variable testing, however, it cannot be referenced until class main is declared

报错引用失败

Answer 1

您可以像调用任何其他静态方法一样调用它：

Echo.main(new String[] { "hello", "world" });

完整会话：

$ jshell
|  Welcome to JShell -- Version 11.0.8
|  For an introduction type: /help intro

jshell> public class Echo {
   ...>     public static void main (String[] args) {
   ...>         for (String s: args) {
   ...>             System.out.println(s);
   ...>         }
   ...>     }
   ...> }
|  created class Echo

jshell> Echo.main(new String[] { "hello", "world" });
hello
world

请注意，您可以按如下方式声明 main 方法：

public static void main(String... args) { ... }

这与 String[] args 语法二进制兼容，但允许您按如下方式调用它：

Echo.main("hello", "world");

运行来自 Jshell 的回显示例

Run echo example from Jshell

java

jshell

运行 来自 Jshell 的回显示例

Run echo example from Jshell

java

jshell

运行来自 Jshell 的回显示例