I make some classification program with weka api of java and I use weka's default contact-lens.arff data set.

I've completed the code and it runs well with one exception.

import weka.core.Instances;
import weka.classifiers.rules.OneR;
import weka.classifiers.trees.J48;
import weka.classifiers.bayes.NaiveBayes;
/*
 ~ some codes ~
*/
    static OneR or_lens = new OneR(); 
    static J48 tree_lens=new J48(); 
    static NaiveBayes nb_lens = new NaiveBayes(); 
    
    static OneR or_weather = new OneR();
    static J48 tree_weather=new J48();
    static NaiveBayes nb_weather = new NaiveBayes(); 
    
    public static void lens_learning(Instances lens_data) {
        
        try {
            or_lens.buildClassifier(lens_data); // occur exception
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
/*
 ~ some codes ~
*/

java.lang.reflect.InaccessibleObjectException: Unable to make protected final java.lang.Class java.lang.ClassLoader.defineClass(java.lang.String,byte[],int,int,java.security.ProtectionDomain) throws java.lang.ClassFormatError accessible: module java.base does not "opens java.lang" to unnamed module @4dcbadb4
    at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:354)
    at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:297)
    at java.base/java.lang.reflect.Method.checkCanSetAccessible(Method.java:199)
    at java.base/java.lang.reflect.Method.setAccessible(Method.java:193)
    at weka.core.WekaPackageClassLoaderManager.injectClasses(WekaPackageClassLoaderManager.java:792)
    at weka.core.WekaPackageClassLoaderManager.injectAllClassesInFromStream(WekaPackageClassLoaderManager.java:690)
    at weka.core.WekaPackageClassLoaderManager.injectMTJCoreClasses(WekaPackageClassLoaderManager.java:118)
    at weka.core.WekaPackageManager.<clinit>(WekaPackageManager.java:255)
    at weka.core.ResourceUtils.readProperties(ResourceUtils.java:241)
    at weka.core.ResourceUtils.readProperties(ResourceUtils.java:184)
    at weka.core.Utils.readProperties(Utils.java:183)
    at weka.core.Capabilities.<clinit>(Capabilities.java:104)
    at weka.classifiers.AbstractClassifier.getCapabilities(AbstractClassifier.java:509)
    at weka.classifiers.rules.OneR.getCapabilities(OneR.java:289)
    at weka.classifiers.rules.OneR.buildClassifier(OneR.java:317)
    at hw2.Hw2.lens_learning(Hw2.java:25)
    at hw2.Hw2.main(Hw2.java:102)

After it occurs this Runtime Exception, program runs smoothly.

But, I want to hide or get rid of this exception strings.

I use jdk-17.0.1.

1. Why buildClassifier occurs this exception?

2. How can I hide this exception strings? try ... catch ... couldn't hide them :,(

CodePudding user response：

At the time of writing, Weka's package manager does not work with Java 16 or later (due to low-level class injections). Use Java 11 instead.