Linux 错误：无法找到或加载主类

Error: Could not find or load main class

提问by Dave

I am having trouble compiling and running my Java code, intended to allow me to interface Java with a shared object for Vensim, a simulation modeling package.

我在编译和运行我的 Java 代码时遇到问题，目的是让我将 Java 与一个仿真建模包 Vensim 的共享对象连接起来。

The following code compiles without error:

下面的代码编译没有错误：

javac -d . -cp ./apache-log4j-1.2.16/log4j-1.2.16.jar:./vensim.jar SpatialModel.java     VensimHelper.java VensimException.java VensimContextRepository.java

However, when I try to run the following:

但是，当我尝试运行以下命令时：

java -cp ./apache-log4j-1.2.16/log4j-1.2.16.jar:./vensim.jar SpatialModel vars

I get the following error: "Error: Could not find or load main class SpatialModel ". My SpatialModel.java code does contain a 'main' method (below), so I'm not sure what the problem is - can anyone please help me out? Thanks.

我收到以下错误：“错误：无法找到或加载主类 SpatialModel”。我的 SpatialModel.java 代码确实包含一个“main”方法（如下），所以我不确定问题是什么 - 任何人都可以帮我吗？谢谢。

import java.io.File;
import java.text.NumberFormat;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import org.apache.log4j.Logger;

public class SpatialModel {

    private VensimHelper vh;

    public static final String DLL_LIBNAME_PARAM = "vensim_lib_nam";

    public static final String MODEL_PATH_PARAM = "vensim_model_path";

    private final static int VENSIM_CONTEXT_CREATION_MAX_FAILURE_COUNT = 10;

    public SpatialModel() throws SpatialException {

        String libName = System.getProperty(DLL_LIBNAME_PARAM);
        String modelPath = System.getProperty(MODEL_PATH_PARAM);        

        if(libName == null || libName.trim().equals("")) {
            log.error("Vensim library name has to be set with -D" + DLL_LIBNAME_PARAM);
            throw new SpatialException("Vensim library name has to be set with -D" + DLL_LIBNAME_PARAM);
        }

        if(modelPath == null || modelPath.trim().equals("")) {
            log.error("Model path has to set with -D" + MODEL_PATH_PARAM);
            throw new SpatialException("Model path ahs to be set with -D" + MODEL_PATH_PARAM);
        }

        for (int i = 0; i < VENSIM_CONTEXT_CREATION_MAX_FAILURE_COUNT && vh == null; i++) {
            try {
                log.info("creating new vensim helper\n\tdll lib: " + libName + "\n\tmodel path: " + modelPath);
                vh = new VensimHelper(libName, modelPath);
            } catch (Throwable e) {
                log.error("An exception was thrown when initializing Vensim, try: " + i, e);
            }
        }
        if (vh == null) {
            throw new SpatialException("Can't initialize Vensim");
        }

    }

    public static void main(String[] args) throws VensimException {

        long before = System.currentTimeMillis();   
        String libName = System.getProperty(DLL_LIBNAME_PARAM);
        String modelPath = System.getProperty(MODEL_PATH_PARAM);

        if (libName == null) {
            libName = "libvensim";
        }
        if(modelPath == null) {
            modelPath = "~/BassModel.vmf";
        }

        System.setProperty(DLL_LIBNAME_PARAM, libName);
        System.setProperty(MODEL_PATH_PARAM, modelPath);

        if (args.length > 0 && args[0].equals("info")) {
            System.out.println(new VensimHelper(libName, modelPath).getVensimInfo());
        } else if (args.length > 0 && args[0].equals("vars")) {
            VensimHelper helper = new VensimHelper(libName, modelPath);
            String[] vars = helper.getVariables();
            for (String var : vars) {
                System.out.println(helper.getVariableInfo(var));
            }
        } else {

            File f = new File(".");
            System.out.println(f.getAbsolutePath());

            SpatialModel sm = new SpatialModel();
        }

        System.out.println("Execution time: " + (System.currentTimeMillis() - before));
    }

}

采纳答案by Saket

You must ensure that you add the location of your .classfile to your classpath. So, if its in the current folder, add .to your classpath. Note that the Windows classpath separator is a semi-colon, i.e. a ;.

您必须确保将.class文件的位置添加到类路径中。因此，如果它在当前文件夹中，请添加.到您的类路径中。请注意，Windows 类路径分隔符是一个分号，即;.

回答by Rafael Cordones

I believe you need to add the current directory to the Java classpath

我相信您需要将当前目录添加到 Java 类路径中

java -cp .:./apache-log4j-1.2.16/log4j-1.2.16.jar:./vensim.jar SpatialModel vars

回答by ymutlu

Problem is not about your main function. Check out for

问题不在于您的主要功能。退房

javac -d . -cp ./apache-log4j-1.2.16/log4j-1.2.16.jar:./vensim.jar SpatialModel.java     VensimHelper.java VensimException.java VensimContextRepository.java

output and run it.

输出并运行它。

回答by Shaddu

If you try to run a java application which needs JDK 1.6 and you are trying to run on JDK 1.4, you will come across this error. In general, trying to run a Java application on old JRE may fail. Try installing new JRE/JDK.

如果您尝试运行需要 JDK 1.6 的 Java 应用程序，并且尝试在 JDK 1.4 上运行，则会遇到此错误。通常，尝试在旧 JRE 上运行 Java 应用程序可能会失败。尝试安装新的 JRE/JDK。

回答by Sudhakar Pabbati

You can try these two when you are getting the error: 'could not find or load main class'

出现错误时，您可以尝试这两个：“无法找到或加载主类”

If your class file is saved in following directory with HelloWorldprogram name d:\sample

如果您的类文件以HelloWorld程序名称 保存在以下目录中d:\sample

1. java -cp d:\sample HelloWorld
2. java -cp . HelloWorld

1. java -cp d:\sample HelloWorld
2. java -cp . HelloWorld

回答by Samsky

Check your BuildPath, it could be that you are referencing a library that does not exist anymore.

检查您的BuildPath，可能是您正在引用一个不再存在的库。

回答by Snekse

I know this question was tagged with linux, but on windows, you might need to separate your cp args with a ;instead of a :.

我知道这个问题是用 linux 标记的，但是在windows 上，您可能需要用 a;而不是 a来分隔您的 cp 参数:。

java -cp ./apache-log4j-1.2.16/log4j-1.2.16.jar;./vensim.jar SpatialModel vars

java -cp ./apache-log4j-1.2.16/log4j-1.2.16.jar;./vensim.jar SpatialModel vars

http://docs.oracle.com/javase/7/docs/technotes/tools/windows/classpath.html

http://docs.oracle.com/javase/7/docs/technotes/tools/windows/classpath.html

回答by user2318595

You have to set the classpath if you get the error:

如果出现错误，则必须设置类路径：

Could not find or load main class XYZ

无法找到或加载主类 XYZ

For example:

例如：

E:\>set path="c:\programfiles\Java\jdk1.7.0_17\bin"
E:\>set classpath=%classpath%;.;
E:\>javac XYZ.java
E:\>java XYZ

回答by cane

If you work in Eclipse, just make a cleanup (project\clean..clean all projects) of the project.

如果您在 Eclipse 中工作，只需project\clean..clean all projects对项目进行清理 ( )。

回答by Maxim Geerinck

I was using Java 1.8, and this error suddenly occurred when I pressed "Build and clean" in NetBeans. I switched for a brief moment to 1.7 again, clicked OK, re-opened properties and switched back to 1.8, and everything worked perfectly.

我使用的是 Java 1.8，当我在 NetBeans 中按下“Build and clean”时突然出现这个错误。我又短暂地切换到 1.7，单击“确定”，重新打开属性并切换回 1.8，一切正常。

I hope I can help someone out with this, as these errors can be quite time-consuming.

我希望我能帮助别人解决这个问题，因为这些错误可能非常耗时。