LINUX下执行.class的java.lang.NoClassDefFoundError解决

最新推荐文章于 2023-09-12 16:00:31 发布

yangzongzhuan

最新推荐文章于 2023-09-12 16:00:31 发布

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本文详细介绍了在Linux环境下运行Java程序时遇到NoClassDefFoundError错误的解决办法，包括检查语法、确保类路径包含当前目录、检查是否正确编译并导入包名等步骤。

一个老外的帖子说的还比较详细:
Most people always have the following problem when run their java programs under linux box:
Exception in thread "main" java.lang.NoClassDefFoundError: *.java
Even though these programs  really have no problem at all.
Here are some solutions for you:
1) Check your syntax that you are trying to run the java class and make sure it should be like this (assume the class file is foo.class):
java  foo      instead of    java  foo.class

2) Make sure your classpath contain the special path ".", actually this is most likely where the problem come from.
You can try to run your program as follows.

java -cp .  foo   or
java  -classpath  .  foo

If it works, then you are suppose to add "." to you classpath.
For example:
export CLASSPATH=.:$JAVA_HOME/lib:JAVA_HOME/jre/lib

3) Check it out if you compiled the java file without specifying the package that import in your file.

What if all these works are done, but your still got the same problem?
Well, in this case, you've got to have a look at your souce code......

Good luck!
前两点虽然有时也导致这个问题, 但是不是问题的关键, 关键是第三点~
但这个家伙的第三点说的很模糊..还好运! 不过倒是起到提示作用~
研究了下, 发现出现这个问题多是由于源代码里面有package名:
源码路径: /home/ymiao/linux_java_project/src

测试代码:
package test;

public class HelloWorld {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        System.out.println("HelloWorld!");
    }

}

字节码文件输出路径: /home/ymiao/linux_java_project/classes

字节码文件所在路径: /home/ymiao/linux_java_project/classes/test/
这个路径下面是HelloWorld.class文件

执行:
1. 如果跑到/home/ymiao/linux_java_project/classes/test/
执行java HelloWorld
输出:
Exception in thread "main" java.lang.NoClassDefFoundError: HelloWorld (wrong name: test/HelloWorld)
2. 如果跑到/home/ymiao/linux_java_project/classes/test/
执行java test.HelloWorld
输出:
Exception in thread "main" java.lang.NoClassDefFoundError: test/HelloWorld
3. 如果跑到/home/ymiao/linux_java_project/classes
执行java test.HelloWorld
输出:
HelloWorld!

结论:
1. 出现wrong name的java.lang.NoClassDefFoundError, 由于执行的时候前面没加package名,
否则就是classpath路径不对, 要指定-cp或者-classpath为字节码输出路径(注意不是字节码文件所在路径, 由于package的存在).
2. 项目中的classpath是Default output folder字节码文件输出路径,而不是字节码文件所在路径
完整的执行命令是:
java -cp 字节码文件输出路径字节码文件的全名(包名.类名,default package没有包名)

java -cp /home/ymiao/linux_java_project/classes test.HelloWorld