如何抛出NoClassDefFoundError [英] How is NoClassDefFoundError thrown

问题描述

我在eclipse中构建了一个名为com.hello的包，我写了一个简单的HelloWorld程序。 Eclipse自动添加package com.hello;在我的程序之上。而HelloWorld.java被放在

  F：\workspace\helloWorld\src\com\hello; 
  

HelloWorld.class已放入

  F：\workspace\helloWorld\bin\com\hello。 
  

它在Eclipse中工作得很好。但是当我进入目录 F：\workspace\helloWorld\bin\com\\hello 并使用命令行java HelloWorld时，我得到 NoClassDefFoundError的。我知道它可能与类路径有关。但是我不太确定。

解决方案

你的课程是在一个包 com.hello 。要运行它，您必须确保您的包中的基本目录是 F：\workspace\helloWorld\bin 案例，在类路径。

尝试运行如下：

  java -cp F：\workspace\helloWorld\bin com.hello.HelloWorld 
  

您也可以转到 F：\workspace\helloWorld\bin 目录，然后使用

  java com.hello.HelloWorld 
  

这将工作，因为Java将使用当前目录作为默认（如果您没有设置 CLASSPATH 环境变量）。

I built a package called "com.hello" in eclipse and I wrote an easy HelloWorld program. Eclipse automatically added "package com.hello;" on top of my program. And HelloWorld.java was put in

F:\workspace\helloWorld\src\com\hello;

HelloWorld.class was put in

F:\workspace\helloWorld\bin\com\hello.

It worked very well in Eclipse. But when I entered the directory "F:\workspace\helloWorld\bin\com\hello" and used command line with "java HelloWorld," I got NoClassDefFoundError. I know it may have something to do with the classpath. But I'm not quite sure.

解决方案

Your class is in a package com.hello. To run it, you must make sure the base directory of the package, which is F:\workspace\helloWorld\bin in your case, is in the classpath.

Try running it like this:

java -cp F:\workspace\helloWorld\bin com.hello.HelloWorld

You can also go to the directory F:\workspace\helloWorld\bin and then run it with

java com.hello.HelloWorld

This will work because Java will use the current directory as the default (if you do not have the CLASSPATH environment variable set).

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