Creating an array to store generic types in Java [duplicate]

The generic info only matters in compile time, it tells the compiler which type could be put into an array, in runtime, all the generic info will be erased, so what matters is how you declare the generic type.

Quoted from Think in Java:

it’s not precisely correct to say that you cannot create arrays of
generic types. True, the compiler won’t let you instantiate an array
of a generic type. However, it will let you create a reference to
such an array. For example:

List<String>[] ls; 

This passes through the compiler without complaint. And although you
cannot create an actual array object that holds generics, you can
create an array of the non-generified type and cast it:

//: arrays/ArrayOfGenerics.java 
// It is possible to create arrays of generics. 
import java.util.*; 

public class ArrayOfGenerics { 
    @SuppressWarnings("unchecked") 
    public static void main(String[] args) { 
        List<String>[] ls; 
        List[] la = new List[10]; 
        ls = (List<String>[])la; // "Unchecked" warning 
        ls[0] = new ArrayList<String>(); 
        // Compile-time checking produces an error: 
        //! ls[1] = new ArrayList<Integer>(); 

        // The problem: List<String> is a subtype of Object 
        Object[] objects = ls; // So assignment is OK 
        // Compiles and runs without complaint: 
        objects[1] = new ArrayList<Integer>(); 

        // However, if your needs are straightforward it is 
        // possible to create an array of generics, albeit 
        // with an "unchecked" warning: 
        List<BerylliumSphere>[] spheres = 
           (List<BerylliumSphere>[])new List[10]; 
        for(int i = 0; i < spheres.length; i++) 
           spheres[i] = new ArrayList<BerylliumSphere>(); 
    } 
}

Once you have a reference to a List[], you can see that you
get some compile-time checking. The problem is that arrays are
covariant, so a List[] is also an Object[], and you can use
this to assign an ArrayList into your array, with no error at
either compile time or run time.

If you know you’re not going to
upcast and your needs are relatively simple, however, it is possible
to create an array of generics, which will provide basic compile-time
type checking. However, a generic container will virtually always be a
better choice than an array of generics.