编译后应用程序无法找到主类

package com.greg.dog;

public class Dog {
    public void bark() {
        System.out.println("bark");
    }
}

package com.greg.dog;

public class TestDog {
   public static void main(String args[]) {
        Dog d = new Dog();
        d.bark();
    }
}

user1@blackpearl:~/Desktop/test/src/com/greg/dog$ javac Dog.java 
user1@blackpearl:~/Desktop/test/src/com/greg/dog$ javac TestDog.java 
TestDog.java:6: cannot find symbol
symbol  : class Dog
location: class com.greg.dog.TestDog
        Dog d = new Dog();
        ^
TestDog.java:6: cannot find symbol
symbol  : class Dog
location: class com.greg.dog.TestDog
        Dog d = new Dog();
                    ^
2 errors

java version "1.6.0_0"
IcedTea6 1.3.1 (6b12-0ubuntu6.7) Runtime Environment (build 1.6.0_0-b12)
OpenJDK 64-Bit Server VM (build 1.6.0_0-b12, mixed mode)

user1@blackpearl:~/Desktop/test/src$ java com/greg/dog/TestDog.java 
Exception in thread "main" java.lang.NoClassDefFoundError: com/greg/dog/TestDog/java
Caused by: java.lang.ClassNotFoundException: com.greg.dog.TestDog.java
    at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:319)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:264)
    at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:332)
Could not find the main class: com/greg/dog/TestDog.java. Program will exit.