我在编译和运行我的Java代码时遇到了麻烦,旨在允许我将Java与Vensim的共享对象进行接口,Vensim是一个仿真建模包。

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

然而,当我试图运行以下:

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

我得到以下错误:“错误:无法找到或加载主要类SpatialModel ”。我的SpatialModel.java代码确实包含一个“main”方法(如下所示),所以我不确定问题是什么-有人能帮帮我吗?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));
    }

}

当前回答

java -verbose:类HelloWorld可能会帮助你了解哪些类正在被加载。

另外,如前所述,记得调用完整的限定名(即include package)。

其他回答

This problem occurred for me when I imported an existing project into eclipse. What happens is it copied all the files not in the package, but outside the package. Hence, when I tried run > run configurations, it couldn't find the main method because it was not in the package. All I did was copy the files into the package and Eclipse was then able to detect the main method. So ultimately make sure that Eclipse can find your main method, by making sure that your java files are in the right package.

问题不在于你的主要职能。检查

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

输出并运行它。

如果遇到这个错误,并且正在使用Maven构建jar,那么很有可能只是在src/main/ Java /中没有Java类。

在我的例子中,我在Eclipse中创建了我的项目,默认为src(而不是src/main/java/)。

所以我最终得到了类似于mypackage.morepackage.myclass的东西,以及类似于src/mypackage/morepackage/myclass的目录结构,这本身没有任何问题。但是当你运行mvn clean install时,它会查找src/main/java/mypackage/morepackage/myclass。它不会找到类,但也不会出错。所以它会成功构建,当你运行输出的Jar时,结果是:

Error: Could not find or load main class mypackage.morepackage.myclass

因为它从来没有将您的类包含在打包的Jar中。

检查您的BuildPath,可能是您正在引用一个不再存在的库。

我在Windows中也有类似的问题,这与类路径有关。从命令行,一直导航到Java文件所在的目录(*. Java和*.class),然后再用命令尝试。