Error: Could not find or load main class?

Question

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\ dll lib: " + libName + "\\n\ model 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

The problem is not in your code, but rather in your IDE. Which IDE are you using? Try googling "Error: Could not find or load main class? in Eclipse" if you're using Eclipse for example. It's typically a setting in your run configuration.

Answer 2

I don't see anything wrong with the code per se but the error seems to be that it can't find the executable in the specified path for some reason. Have you examined the library to make sure the executable was compiled where you thought it was?