java: generic array creation error

The line of code below incurs a generic array creation error at compile time.

       ArrayList<String>[] sc = new ArrayList<String>[2];

The following code compiles, but it will generate an unchecked cast warning at compile time.

      ArrayList<String>[] sc = (ArrayList<String>[]) new Object[2];

However, if you cast an already built Object array to an ArryList<String>[] and if the array contains object other than ArrayList<String> a ClassCastException will happen at execution time.

        Object[] test = new Object[2];
        test[0] = new ArrayList<String>();
        test[1] = new Integer(9);
        ArrayList<String>[] sc = (ArrayList<String>[])test;

The following code compiles, but gives an unchecked cast warning at compile time. If you don't want to see the warning message, you can supress it.

      @SuppressWarnings("unchecked")
      ArrayList<String>[] sc = (ArrayList<String>[])Array.newInstance(String.class, 2);
or
      ArrayList<String>[] sc = (ArrayList<String>[]) new ArrayList[2];

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