java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [Ljava.lang.Class;

Question

when I'm executing the below code I'm getting Class cast exception. I believe in an object is trying to cast with class can anyone help me

 public abstract AGridFilterMenu refreshFilters();


 public AGridFilterMenu supportFilter(String style, Class<? extends AFilterItem> clazz, By... childLocators) {
      ArrayList<Class<By>> signature = new ArrayList<>();
      for(int i = 0; i< childLocators.length; i++) {
          signature.add(By.class);
      }

      try {
        Constructor<? extends AFilterItem> construct = clazz.getConstructor((Class<?>[]) signature.toArray());
        constructors.put(style, construct);
        filteritemChildLocators.put(style, childLocators);
    } catch (NoSuchMethodException | SecurityException e) {
        throw new TestCodeException("Unsupported FilterItem signature", e);
    }
      return this;
  }

  public AFilterItem getFilter(String filterName) {
    logger.trace(String.format("Retrieving filter %s", filterName));
    AFilterItem item = filters.get(filterName);`enter code here`
    item.bind();
    return item;
  }

Please [edit] your post and add the COMPLETE stack trace; indicate which statement in your code throws the exception. — Jim Garrison, Jul 31 '18 at 05:35
Please provide exact error an also mention on which line you are getting exception.. — DhaRmvEEr siNgh, Jul 31 '18 at 05:35
Please share your debugging details, people here can help you more clearly if you stage your question more clearly. — Simmant, Jul 31 '18 at 05:43

score 1 · Accepted Answer · answered Jul 31 '18 at 06:11

1

The problem is method Object[] List.toArray() returns an array of Object and it cannot be cast to array of Class<?>.

Luckily, there's a more suitable method T[] List.toArray(T[]), but you need to prepare an array instance of particular size and type to store the result.

Keep in mind that in case of ArrayList both argument and returning value are the same instance of array, which is mutating inside the toArray method.

Class<?>[] signatureArray = new Class<?>[signature.size()];
signature.toArray(signatureArray);
Constructor<? extends AFilterItem> construct = clazz.getConstructor(signatureArray);

answered Jul 31 '18 at 06:11

diziaq

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You do not have to prepare a size matching array. It's just better performance, because a size matching array is used directly. Otherwise, a size matching array is created. I use either a constant zero sized array or indeed a new size matching array. – jokster Jul 31 '18 at 07:58
@jokster, you're right - the precise contract of the method is in javadoc. – diziaq Jul 31 '18 at 13:44

java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [Ljava.lang.Class;

1 Answers1