CODEWITHSUNDEEP
java
zeynep
zeynep

Reputation: 71

Generic array creation via own class

To create array of generic, I have seen below recommendation in many websites including this one, too. However, I wonder why we do not use directly the generic class in array creation. What is the reason to push us to not use below array creation method?

What currently is used 

public class X<T>  {

    private Y<T> tTypeClass = null;

    public T[] Array() {       
        T[] array = (T[]) Array.newInstance(tTypeClass.getObject().getClass(),4); 
    }
}

Why we do not use 

public class X<T>  {

    public T[] arrayCreation() {       
        T[] array = (T[]) Array.newInstance(this.getClass(),4); 
    }
}

Upvotes: 1

Views: 56

Answers (2)

sp00m
sp00m

Reputation: 48837

Because the cast is not safe. For example:

String[] s = new X<String>().arrayCreation();

will result in java.lang.ClassCastException.

Upvotes: 0

David Xu
David Xu

Reputation: 5607

You can't write code like T[] arr = new T[xx] because Java generics are type-erased. The Runtime has no idea what T is during runtime, because the Java compiler replaced all generics with casts at compile time.

Also,

public class X<T>  {

    public T[] arrayCreation() {       
        T[] array = (T[]) Array.newInstance(this.getClass(),4); 
    }
}

will cause a ClassCastException because it creates an array of X[] and tries to cast it to T[].

Upvotes: 1

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