不确定 NoClassDefFoundError 背后的原因

Question

我构建了一个 DLL，我试图用它包装 Java 代码，但是我在运行宁我的 Java 程序时遇到了一些问题。我写了一个简单的测试 DLL 和 Java 程序并产生了同样的错误，虽然网上有很多关于 NoClassDefFoundError 的资源，但我似乎无法用任何故障排除方法解决我的问题。

这是我的 D:\Test1.Java 文件

public class Test1 { 

    static {
        //System.loadLibrary("HeyLand");
        System.load("D://HeyLand.dll");
    }

    public native void displayHeyLand();

    public static void main (String[] args) {
        Test1 t = new Test1();
        t.displayHeyLand();
    }
}

编译后，尝试运行 D:\Test1.class 结果如下：

D:\>java Test1.class
Exception in thread "main" java.lang.NoClassDefFoundError: Test1.class
Caused by: java.lang.ClassNotFoundException: Test1.class
        at java.net.URLClassLoader.findClass(URLClassLoader.java:434)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:660)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:358)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:626)
Could not find the main class: Test1.class.  Program will exit.

为什么我被难住了：
1. 我已将我的 class 路径设置为 D:\，所以我相信我的 class 定义会在 class 路径中，但我看不到我的编译方式- time 和运行-time classpaths 可能有任何不同。
2. 我看不出这与静态初始化有什么关系，我相信异常看起来会有所不同。

也许我只是遗漏了一些非常简单的东西，我是 Java 的新手。

非常感谢任何帮助！

Answer 1

classpath 环境变量优先于 java 运行命令中的环境变量。您需要指定 class 位置（以及删除 .class 文件扩展名）

java -cp . Test1

Answer 2

Java normal syntax for executing class file is 
Java [<options>....} <class-name> [<arguments>....]


For example 

java com.package.name.Test1

here how compiler works

1. Compiler search for complete class name
2. Load that class
3. check for main method - in the same class
4. Call main method with passed arguments in command line string.



Now following are the possibilities why your class may not found main method.
1 - forgot to include package name
    I am new developer in java but I found when I run application using eclips or intellJ editor it gives different path and package name and execute code as I noticed it on command line edior. So make sure you are including package name 

    For example:
    java com.package.name.Test1 instead of 
    java Test1 

2. File name or pathname rather then class name
   As I noticed output file is in different location. That why class file path was different.
   java Test1.class
   java com/package/name/Test1.class

3. Typo


also I noticed you are using 
  static {
        //System.loadLibrary("HeyLand");
        System.load("D://HeyLand.dll");
    }


 Is this function ? or constructor? If it is function then where is name of the function? You cant write code without any reference in classs

不确定 NoClassDefFoundError 背后的原因

Unsure about reason behind NoClassDefFoundError

java

command

classpath

noclassdeffounderror

runtimeexception