classpath不默认为当前目录 [英] classpath does not default to current directory

问题描述

我在Java中编写并编译了一个简单的Hello World程序，但是当我尝试运行它时，我遇到了错误消息错误：无法找到或加载主类Hello 。它只是在我执行命令 java -cp之后。 Hello 它已成功运行。

I wrote and compiled a simple Hello World program in Java but when I tried to run it I was greeted with the error message Error: Could not find or load main class Hello. It was only after I executed the command java -cp . Hello that it successfully ran.

奇怪的是，当前目录似乎已成为类路径的一部分。脚本

Oddly enough, the current directory already seems to be part of the classpath. The script

class CheckClassPath{
    public static void main(String args[]){
        System.out.println(System.getProperty("java.class.path"));
    }
}

打印。，但我必须再次明确设置 classpath 选项。

prints ., though I again have to explicitly set the classpath option.

有没有人知道为什么这发生了什么？我正在使用Ubuntu 16.04和open-JDK 1.8版。

Does anyone have an idea why this is happening? I am using Ubuntu 16.04 and open-JDK version 1.8.

推荐答案

我希望 CLASSPATH 已设置环境变量。运行 echo $ CLASSPATH 查看它的设置。

I expect that a CLASSPATH environment variable has been set. Run echo $CLASSPATH to see what it is set to.

如果你不使用 -jar 选项然后：

If you don't use the -jar option then:

• 如果有 -cp ，指定类路径


• 否则，如果在环境中设置 CLASSPATH ，则指定类路径


• 否则默认类路径为。使用。

• If there is a -cp, that specifies the classpath
• Else if CLASSPATH is set in the environment, that specifies the classpath
• Else a default classpath of "." is used.

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