Java class execution problem: java.lang.ClassNotFoundException

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$1.run(URLClassLoader.java:217)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.jav开发者_StackOverflowa:205)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
    at sun.misc.Launcher$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. :)

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.

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

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.