Doubt in ArrayList's toArray function

[J Bolla]

 
 
import java.util.*;
 

public class Coll {
 
public static void main (String [] args) {
 
ArrayList list = new ArrayList ();
list.add(new Integer(1));
list.add(new Integer(2));
list.add(new Integer(3));
 
Integer [] intArray = new Integer[list.size()];
intArray = (Integer[])list.toArray(intArray);  //1st statement
//intArray = (Integer[])list.toArray();  //2nd statement
 
System.out.println(list);
for (int i=0; i<intArray.length; i++)
System.out.println(intArray[i]);
 
}
 
}
 
 

Both the toArray functions of the ArrayList return Object[] but the commented
line gives a runtime exception. We know that arrays cant be upcasted like the
regular datatypes.

This :

 
list.toArray(intArray);

is identical to

 
intArray = (Integer[])list.toArray(intArray);

So it seems that the assignment and casting is redundant in the
first statement.

[KasiMurugan Ramasamy]

Hi

toArray( RunTimeType[] ), RunTimetype type might be any type which can be cast for the arrayList elements.

In ur case toArray(Integer[])it converts the arrayList elements into Integer Array elements.

But Object[] toArray() returns Object Array, so you can't downcast the SuperType to SubType

More please read, collection's toArray(Object[]) and toArray().
I hope you get me.