java - 在不编译的情况下运行 Java 程序

Question

最近装了Java 11，写代码的时候不小心把Main.java编译成javac Main.java，写成了java Main.java 。它没有向我显示任何错误，并且没有任何问题地解决了问题。为什么会这样？这是较新版本的 Java 中的新功能吗？

Main.java 的内容:

public class Main {
    public static void main(String[] args) {
        System.out.println("Hello, World!");
    }
}

在 Java 8 中运行:

java version "1.8.0_112"
Java(TM) SE Runtime Environment (build 1.8.0_112-b16)
Java HotSpot(TM) 64-Bit Server VM (build 25.112-b16, mixed mode)

>>> java Main.java
Error: Could not find or load main class Main.java

在 Java 11 中运行:

java version "11.0.1" 2018-10-16 LTS
Java(TM) SE Runtime Environment 18.9 (build 11.0.1+13-LTS)
Java HotSpot(TM) 64-Bit Server VM 18.9 (build 11.0.1+13-LTS, mixed mode)

>>> java Main.java
Hello, World!

Answer 1

此功能作为 JEP 330 的一部分引入:启动单文件源代码程序。

In source-file mode, the effect is as if the source file is compiled into memory, and the first class found in the source file is executed. For example, if a file called HelloWorld.java contains a class called hello.World, then the command

java HelloWorld.java is informally equivalent to

javac -d HelloWorld.java java -cp hello.World

这是 JEP