java在使用CSVLoader时未指定源

Question

在我的Java代码中，我试图将一个.csv文件读入一个.arff文件，为此我使用了CSVLoader。下面是我的代码：

package processingPackage;

import java.io.File;
import java.io.IOException;

import weka.core.Instances;
import weka.core.converters.CSVLoader;


public class GenerateArffDetails {

    /*filePath in the following line*/
    /*"/Users/SubrataMohanty/Desktop/customer_loan_details.csv"*/
    public String getTrainFilePath (String filePath) throws IOException {

            System.out.println(filePath);
            CSVLoader loader = new CSVLoader();
            loader.setSource(new File(filePath));

            System.out.println(filePath);
            Instances dataStructure = loader.getStructure();
            Instances data = loader.getDataSet();

            weka.core.converters.ArffSaver saver = new weka.core.converters.ArffSaver();

            saver.setInstances(data);
            saver.setFile(new File("/Users/SubrataMohanty/Desktop/customer_loan_details.arff"));
            saver.writeBatch();

            String path = "/Users/SubrataMohanty/Desktop/customer_loan_details.arff";
            return (path);
        }
}

在执行上述代码时，我不断得到以下错误跟踪

java.io.IOException: No source has been specified
    at weka.core.converters.CSVLoader.getStructure(CSVLoader.java:962)
    at processingPackage.GenerateArffDetails.getTrainFilePath(GenerateArffDetails.java:19)
    at processingPackage.LoanClassifier.classifyLoanApplicant(LoanClassifier.java:23)
    at processingPackage.Driver.classifyApplicants(Driver.java:15)
    at processingPackage.RunClassifier.doGet(RunClassifier.java:38)
    at processingPackage.RunClassifier.doPost(RunClassifier.java:48)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:661)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:478)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:80)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:650)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:799)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1457)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)

我以以下字符串变量格式传递filePath变量：

"/Users/SubrataMohanty/Desktop/customer_loan_details.csv"

在进一步阅读CSVLoader类时，我偶然发现了m_sourceReader变量，该变量初始化如下：

m_sourceReader = new BufferedReader(new InputStreamReader(input));

如果上面的异常有null，我不理解，因为我显然传递了一个正确的filePath，则返回该异常。那么我的错误是什么呢

我可以知道如何解决这个问题吗

注意：我正在为我的项目在MacOSX Sierra上工作