Java开发网 - 帮忙啊,出人命了啊!急(NoClassDefFoundError)

Topic: 帮忙啊,出人命了啊!急(NoClassDefFoundError)

1.帮忙啊,出人命了啊!急(NoClassDefFoundError)

Posted by: ncie
Posted on: 2007-04-24 09:49

出错信息:Exception in thread "main" java.lang.NoClassDefFoundError: Hello

系统是WINXP-SP2
D:\java\JAVA\例题\第01章例题\例1.1>javac Hello.java

D:\java\JAVA\例题\第01章例题\例1.1>java Hello
Exception in thread "main" java.lang.NoClassDefFoundError: Hello

D:\java\JAVA\例题\第01章例题\例1.1>echo %classpath%
.:c:\Program Files\Java\jdk1.5.0_11\lib;c:\Program Files\Java\jdk1.5.0_11\lib\to
ols.jar;c:\Program Files\Java\jdk1.5.0_11\lib\dt.jar

一开始没加c:\Program Files\Java\jdk1.5.0_11\lib,后来在网上看有这个就加了,也不行...
D:\java\JAVA\例题\第01章例题\例1.1>echo %path%
C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\Wbem;c:\Program Files\Java\jd
k1.5.0_11\bin

D:\java\JAVA\例题\第01章例题\例1.1>echp %java_home%
'echp' 不是内部或外部命令，也不是可运行的程序
或批处理文件。

D:\java\JAVA\例题\第01章例题\例1.1>echo %java_home%
c:\Program Files\Java\jdk1.5.0_11

D:\java\JAVA\例题\第01章例题\例1.1>java -version
java version "1.5.0_11"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_11-b03)
Java HotSpot(TM) Client VM (build 1.5.0_11-b03, mixed mode, sharing)

D:\java\JAVA\例题\第01章例题\例1.1>

Hello.java 内容如下

public class Hello
{
public static void main(String args[])
{
System.out.println("Hello!");
}
}

执行出错...............................................................
麻烦大家帮帮啊,真要人命啊,就是运行不了啊

2.Re:帮忙啊,出人命了啊!!!!急急 [Re: ncie]	Copy to clipboard
Posted by: Jcat Posted on: 2007-04-24 11:30 .:c:\Program Files\Java\jdk1.5.0_11\lib;c:\Program Files\Java\jdk1.5.0_11\lib\to Please confirm your first colon (the red one) which is supposed to be a semicolon ( ; ) FYI. Whenever you meet the java.lang.NoClassDefFoundError, please check your classpath once and again.

3.Re:帮忙啊,出人命了啊!!!!急急 [Re: ncie]	Copy to clipboard
Posted by: gfiargw Posted on: 2007-04-24 23:14 d:\java\jdk1.6.0_01\bin;%SystemRoot%\system32;%SystemRoot%;%SystemRoot%\System32\Wbem JAVA安装路径放在变量值的前面

4.Re:帮忙啊,出人命了啊!急(NoClassDefFoundError) [Re: ncie]	Copy to clipboard
Posted by: ranchgirl Posted on: 2007-04-27 11:57 帮忙啊,出人命了啊! Police department, please!

5.Re:帮忙啊,出人命了啊!急(NoClassDefFoundError) [Re: ncie]	Copy to clipboard
Posted by: caoyuwu Posted on: 2007-05-02 21:20 java -cp . Hello

6.Re:帮忙啊,出人命了啊!急(NoClassDefFoundError) [Re: ncie]	Copy to clipboard
Posted by: xiezhuojun2006 Posted on: 2007-05-03 23:21 你的情况跟我刚写的时候一样可能是环境变量设定错了我的环境变量是 classpath: .;c:\Program Files\Java\jdk1.5.0_11\lib path: .;c:\Program Files\Java\jdk1.5.0_11\lib.;c:\Program Files\Java\jdk1.5.0_11\bin

7.Re:帮忙啊,出人命了啊!急(NoClassDefFoundError) [Re: ncie]	Copy to clipboard
Posted by: zhuhairubbish Posted on: 2007-05-04 15:35 老兄，不要把JDK安装在如c:\Program Files\路径中有空格的文件目录下，否则后果很严重，试试装在其他目录下吧，肯定行的！

8.Re:帮忙啊,出人命了啊!急(NoClassDefFoundError) [Re: xiezhuojun2006]

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Posted by: why
Posted on: 2007-05-13 04:49

xiezhuojun2006 wrote:
你的情况跟我刚写的时候一样
可能是环境变量设定错了
我的环境变量是
classpath:
.;c:\Program Files\Java\jdk1.5.0_11\lib
path:
.;c:\Program Files\Java\jdk1.5.0_11\lib.;c:\Program Files\Java\jdk1.5.0_11\bin

c:\Program Files\Java\jdk1.5.0_11\lib. is wrong!
c:\Program Files\Java\jdk1.5.0_11\lib is unnecessary

9.Re:帮忙啊,出人命了啊!急(NoClassDefFoundError) [Re: ncie]

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Posted by: JiafanZhou
Posted on: 2007-05-14 20:56

Every Java program has at least three class loaders:

i) The bootstrap class loader
loads the system classes(typically, from the *rt.jar*)
It is an integral part of the JVM and is usually implemented in C.

There is no ClassLoader object corresponding to the bootstrap class loader.
(e.g. String.class.getClassLoader() returns null)

ii) The extension class loader
loads the *standard extension* from the *jre/lib/ext* directory.

You can drop jar files into that directory and the extension class loader will
find the classes in them, even without any classpath.

iii) The system class loader(also known as application class loader)
loads the application classes. It locates classes in the directories and /JAR/ZIP
files on the classpath., as set by the classpath envrionment variable or the
-classpath command-line option.

The classpath system environment only refers to the iii) point which I mentioned above, so lib is unnecessary.

Regards,
Jiafan