Java generics are an interesting thing.

Because of the generic erase (erasure), any operation that needs to know the exact type of information at run time will not work.

public class Erased<t> {private final int SIZE = 100;                  public static void F (Object arg) {if (arg instanceof T) {}//error t var = new T ();    Error t[] array = new T[size]; Error t[] array = (t[]) new object[size]; Unchecked Warning}

Look at the code above, "Arg instanceof T", and the compiler will think that the person writing this program wants to check if ARG is a class. But Erasure caused the man's wish to fail, so he set the sentence to error.

Java generics are an interesting thing.