System.arraycopy

[mirko74]

In Java you can copy an array into another using the normal assignment operator =
public class ArrayTest {
public static void main (String[] args) {
Object[] ov;
String[] sa = {"Green", "Blue", "Red"};
ov = sa;
System.out.println("Color = "+ov[1]);
}
}
So why and when should I use the System.arraycopy ?
Moreover, why in Java ov = ... is not the same as ov[0]= like in C++?

[Naveen Sharma]

Hi Mirko
Here What r u doing is using the same object but with diffrent refrence variable ov,sa. Basically this is a wide conversioning.You r storing an String object refrense in an Object type variable. You have not copy the contents. but you r using the contents by two diffrent refrence names
But arrayCopy function basically copies the contents of two objects(array), from source to destination.
In former case you r taking the same object but two refrences pointing to the same object
but later is for two objects.
Hope u can understand Now

[Angela Lamb]

So why and when should I use the System.arraycopy?

public static void arraycopy(Object�src,
int�src_position,
Object�dst,
int�dst_position,
int�length)


You can see that System.arraycopy has arguments for specifying the position in the array to copy from/to and the length of the copy. Using the normal assignment operator, that would have to be done by looping through the arrays. It is just a matter of writing less code when you only want to copy part of an array.