如何使用包名运行java类 [英] how to run the java class with has package name

问题描述

我有两个java类如下：

I have the two java class as follows:

1。

none package class
System.out.println("App1 hello world...");

2。

has package
package java.java.package1;

System.out.println("App1 hello world...");

然后，我编译并运行它们，结果如下：

then,I compile and run them,the result as follows:

D:\javaTest>javac App1.java

D:\javaTest>javac App2.java

D:\javaTest>java App1
App1 hello world...

D:\javaTest>java java.java.package1.App2

Exception in thread "main" java.lang.NoClassDefFoundError: java/java/package1/Ap
p2
Caused by: java.lang.ClassNotFoundException: java.java.package1.App2
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
Could not find the main class: java.java.package1.App2.  Program will exit.

那么如何运行App2类？

so how to run the App2 class?

推荐答案

您应该使用 -d 选项进行编译，以便这些类最终位于适当的目录层次结构中：

You should compile using the -d option so that the classes end up in an appropriate directory hierarchy:

javac -d . App2.java
java java.java.package1.App2

此外，你不应该首先使用以 java 开头的包名。

Also, you shouldn't use a package name starting with java in the first place.

此外，如果您放置源在适当的目录层次结构中，并从层次结构的根目录编译/运行，您不会遇到此问题。

Also, if you put the source in an appropriate directory hierarchy, and compile/run from the root of the hierarchy, you wouldn't have this problem.

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