Why is my code not working? IBM Watson Language Translation in Java

Question

i need some help with my code. I just recently started learning Java, and I want to make a some kind of language translator with IBM Watson Language Translator api in the future. Code below is just for displaying all available languages, but it doesn't work and below the code are also errors when starting the program. In the IDE it doesn't display any error messages when writing the code. Thanks for any answers.

Code:

import com.ibm.cloud.sdk.core.security.IamAuthenticator;
import com.ibm.watson.language_translator.v3.LanguageTranslator;
import com.ibm.watson.language_translator.v3.model.IdentifiableLanguages;

public class Main {
    public static void main(String[] args) {
    //Where it now says "myApiKey" is in real code my api key
    IamAuthenticator authenticator = new IamAuthenticator("myApiKey");
    LanguageTranslator languageTranslator = new LanguageTranslator("2018-05-01", authenticator);
    //Where it now says "myServiceUrl" is in real code my service url
    languageTranslator.setServiceUrl("myServiceUrl");

    IdentifiableLanguages languages = languageTranslator.listIdentifiableLanguages()
            .execute().getResult();

    System.out.println(languages);
  }
}

Error on start:

Exception in thread "main" java.lang.reflect.InaccessibleObjectException: Unable to make field private java.lang.String java.lang.Throwable.detailMessage accessible: module java.base does not "opens java.lang" to unnamed module @41b388f2
    at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:357)
    at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:297)
    at java.base/java.lang.reflect.Field.checkCanSetAccessible(Field.java:177)
    at java.base/java.lang.reflect.Field.setAccessible(Field.java:171)
    at com.google.gson.internal.reflect.UnsafeReflectionAccessor.makeAccessible(UnsafeReflectionAccessor.java:44)
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.getBoundFields(ReflectiveTypeAdapterFactory.java:159)
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.create(ReflectiveTypeAdapterFactory.java:102)
    at com.google.gson.Gson.getAdapter(Gson.java:458)
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.createBoundField(ReflectiveTypeAdapterFactory.java:117)
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.getBoundFields(ReflectiveTypeAdapterFactory.java:166)
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.create(ReflectiveTypeAdapterFactory.java:102)
    at com.google.gson.Gson.getAdapter(Gson.java:458)
    at com.google.gson.Gson.fromJson(Gson.java:931)
    at com.ibm.cloud.sdk.core.util.ResponseUtils.getValue(ResponseUtils.java:149)
    at com.ibm.cloud.sdk.core.util.ResponseConverterUtils$6.convert(ResponseConverterUtils.java:137)
    at com.ibm.cloud.sdk.core.security.TokenRequestBasedAuthenticator$2.run(TokenRequestBasedAuthenticator.java:320)
    at java.base/java.lang.Thread.run(Thread.java:831)