Generics, arrays, and the ClassCastException

Question

I think there must be something subtle going on here that I don\'t know about. Consider the following:

public class Foo {
  private T[] a = (T[]) ne         


        

Answer 1

@matt b: Thanks for the answer! Very helpful.

I have found a workaround for those interested: give the getA method an initialized array to populate. That way the type info is available.

public class Foo {
  private T[] a = (T[]) new Object[5];

  public Foo() {
    // Add some elements to a
  }

  public T[] getA(T[] holdA) {
    // Check whether holdA is null and handle it...then:
    holdA = (T[]) Array.newInstance(holdA.getClass().getComponentType(), a.length);
    System.arraycopy(a, 0, holdA, 0, a.length);
    return holdA;
  }
}

Then for your main method:

public static void main(String[] args) {
  Foo f = new Foo();
  Double[] a2 = new Double[1];
  a2 = f.getA(a2);
}