Java类执行问题：java.lang.ClassNotFoundException

Question

Below is what I tried in linux terminal: compiled Test.java, run Test.class, and got an error. Then, I tried the same command with "-classpath ." option and "-cp ." option, but also failed.

/testpackage$ cat Test.java 
package testpackage;

public class Test {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        System.out.println("May I take your order?");
    }

}
/testpackage$ javac Test.java 
/testpackage$ java testpackage.Test
Exception in thread "main" java.lang.NoClassDefFoundError: testpackage/Test
Caused by: java.lang.ClassNotFoundException: testpackage.Test
    at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
Could not find the main class: testpackage.Test. Program will exit.

/testpackage$ java -cp . testpackage.Test
Exception in thread "main" java.lang.NoClassDefFoundError: testpackage/Test
Caused by: java.lang.ClassNotFoundException: testpackage.Test
    at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
Could not find the main class: testpackage.Test. Program will exit.

/testpackage$ java -classpath . testpackage.Test
Exception in thread "main" java.lang.NoClassDefFoundError: testpackage/Test
Caused by: java.lang.ClassNotFoundException: testpackage.Test
    at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
Could not find the main class: testpackage.Test. Program will exit.
/testpackage$ 

But if I remove the package "testpackage" and recompile the source code, the resulting class file is executed well.

/testpackage$ cat Test.java
//package testpackage;

public class Test {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        System.out.println("May I take your order?");
    }

}
/testpackage$ javac Test.java
/testpackage$ java Test
May I take your order?
/testpackage$

What's wrong with my code, or execution command? Please help me. Thank you. :)

Answer 1

You need to run the commands from one directory higher.

A class in package foo must live in directory foo . Package foo.bar must be in directory foo/bar and so on.

So, your structure should have a file called /path/to/code/testpackage/Test.java and your working directory should be /path/to/code . You can then run:

javac testpackage/Test.java

java -cp . testpackage.Test

and everything should work.

Answer 2

When you have a package name, the fully resolved class name is testpackage.Test . That's what java.exe expects to see.

Answer 3

You can't work with "testpackage" as your current directory. You would need to run it as

java testpackage.Test

from the directory of which "testpackage" is a subdirectory.