如何在LINUX上设置环境变量CLASSPATH和NoClassDefFoundError

Question

I've been studying classpaths and came across a question. I used the code below:

class AAA 
{
    public AAA() 
    {
        System.out.println("AAA");
    }
}
class BBB 
{
    public BBB() 
    {
        System.out.println("BBB");
    }
}
class ABMain 
{
    public static void main(String[] args) 
    {
        AAA aaa=new AAA();
        BBB bbb=new BBB();
    }
}

On terminal, I did:

1. javac ABMain.java
2. mkdir sub
3. set CLASSPATH=.:.\\sub;
4. move AAA.class .\\sub\\AAA.class
5. move BBB.class .\\sub\\BBB.class
6. java ABMain

When I checked the sub directory, I found that AAA.class and BBB.class were correctly moved, but when I try to run ABMain, I get the following:

Exception in thread "main" java.lang.NoClassDefFoundError: AAA at ABMain.main(ABMain.java:17) Caused by: java.lang.ClassNotFoundException: AAA at java.net.URLClassLoader.findClass(URLClassLoader.java:381) at java.lang.ClassLoader.loadClass(ClassLoader.java:424) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:335) at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ... 1 more

Could you please comment on what I should change to make it work? Thank you in advance.

Answer 1

You need to import the package of sub in before ABMain class because how your ABMain would be able to know the location of AAA and BBB

I would suggest use before AAA Class and BBB class

package sub;

and import package by writing below code before ABMain class

import sub.*;

Answer 2

According to title, you use LINUX. But your steps are for windows ecosystem. To correct the example, you should use direct slash as path delimiter, and add current dir as CLASSPATH alternative (to be able to load main class as well):

1. javac ABMain.java
2. mv AAA.class ./sub/AAA.class
3. mv BBB.class ./sub/BBB.class
4. java -cp ./sub:. ABMain