为什么错误名称与NoClassDefFoundError [英] why wrong name with NoClassDefFoundError

问题描述

我在文件夹 UtilityPack 中创建了一个 List.java 文件，其中包含此代码

I created a List.java file in folder UtilityPack which contains this code

package Utilities;
public class List
{
    private class node{}
    public void insert(int data){}
    public void print(){}
    public static void main(String[] s){}
}

/ p>

To compile i did

C:\UtilityPack>javac List.java

但是当我尝试运行

C:\UtilityPack>java -classpath . List

或

C:\UtilityPack>java List

我收到错误

Exception in thread "main" java.lang.NoClassDefFoundError: List (wrong name: Uti
lities/List)
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:791)
        at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:14
2)
        at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
        at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:423)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:356)
        at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:482)

我一直在尝试执行这个程序从最近3个小时，但没有任何工作。请帮助

I have been trying to execute this program from last 3 hours but nothing worked..please help

推荐答案

您需要完全合格名称例如

You need the fully qualified name e.g.

java -cp . Utilities.List

ie。你正在告诉JVM从一个类 Utilities.List 的当前直接（ -cp。）中查看，在文件 Utilities\List.class 中将会期待。

i.e. you're telling the JVM to look from the current direct (-cp .) for a class Utilities.List, which it will expect in the file Utilities\List.class.

为了更一致，您应该将.java文件在实用程序目录下（是 - 这是tautologous - 包指定这个，但它是一贯的做法）。

To be more consistent you should put the .java file under a Utilities directory (yes - this is tautologous - the package specifies this, but it's consistent practise).

我也会避免调用你的课程 List 。在某些阶段，您将导入一个 java.util.List ，这一切都会令人困惑！

I would also avoid calling your class List. At some stage you're going to import a java.util.List and it'll all get very confusing!

最后，一旦您获得了几个课程，请调查 ant 或另一个构建工具，并单独您的来源和目标目录。

Finally, as soon as you get more than a couple of classes, investigate ant or another build tool, and separate your source and target directories.

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