hello world失败！

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package javaapplicationtest;
//import java.io.*;
/**
 *
 * @author Administrator
 */
public class JavaApplicationTest {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        // TODO code application logic here
        System.out.println("Hello World!");
    }
}

使用java命令运行后：

Exception in thread "main" java.lang.NoClassDefFoundError: JavaApplicationTest (wrong name: javaapplicationtest/JavaAppl
icationTest)
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(Unknown Source)
        at java.security.SecureClassLoader.defineClass(Unknown Source)
        at java.net.URLClassLoader.defineClass(Unknown Source)
        at java.net.URLClassLoader.access$100(Unknown Source)
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.launcher.LauncherHelper.checkAndLoadMain(Unknown Source)

在netbeans里面可以正常地输出：Hello World!

JDK路径：E:\Java\jdk1.7.0_40
JRE路径：D:\Java\jre7
OS分区：D: jdk
[解决办法]
eclipse里的编译环境你设置好了么