Error: Could not find or load main class [duplicat

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• What does “Could not find or load main class” mean? 41 answers

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.

The following code compiles without error:

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:

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.

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));
    }

}

Answer 1

If so simple than many people think, me included :)

cd to Project Folder/src/package there you should see yourClass.java then run javac yourClass.java which will create yourClass.class then cd out of the src folder and into the build folder there you can run java package.youClass

I am using the Terminal on Mac or you can accomplish the same task using Command Prompt on windows

Answer 2

Problem is not about your main function. Check out for

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.

Answer 3

I use Anypoint Studio (an Eclipse based IDE). In my case everything worked well, until I found out that while running the java code, something totally different is executed. Then I have deleted the .class files. After this point I got the error message from this question's title. Cleaning the project didn't solve the problem.

After restarting the IDE everything worked well again.

Answer 4

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

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

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

Answer 5

You have to include classpath to your javac and java commands

javac -cp . PackageName/*.java
java -cp . PackageName/ClassName_Having_main

suppose you have the following

Package Named: com.test Class Name: Hello (Having main) file is located inside "src/com/test/Hello.java"

from outside directory:

$ cd src
$ javac -cp . com/test/*.java
$ java -cp . com/test/Hello

• In windows the same thing will be working too, I already tried

Answer 6

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

Could not find or load main class XYZ

For example:

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