JQ+ Arrays[0]++

[Dominic Mack]

public class TestClass
{
public static void main(String args[ ] )
{
int i = 1;
int[] iArr = {1};
incr(i) ;
incr(iArr) ;
System.out.println( "i = " + i + " iArr[0] = " + iArr [ 0 ] ) ;
}
public static void incr(int n ) { n++ ; }
public static void incr(int[ ] n ) { n [ 0 ]++ ; }
}

I thought arrays were objects and the ++ operator only worked with primatives... so why can you use the ++ operator on a array object element?

[Manish Hatwalne]

 

Originally posted by Dominic Mack:
I thought arrays were objects and the ++ operator only worked with primatives... so why can you use the ++ operator on a array object element?

Array is an object, but 0^th element of the array is an int, which is a primitive. The unary operator ++ works on this int value, which happens to be the 0^th element of an array.
HTH,
- Manish

[This message has been edited by Manish Hatwalne (edited October 12, 2001).]

[Dominic Mack]

If the unary operator works on an int like you said, and
go() returns an int, why can't I do this???
int i = this.go()++;
[This message has been edited by Dominic Mack (edited October 12, 2001).]

[Nain Hwu]

postfix or prefix increment works for variables only.
An element of array is evaluated to a "variable", while
a call to a method is evaluated to what is returned.
Since go() returns an int "value", you can't apply ++
to it.
Here is a quote from JLS:

JLS 15.13 -
The result of an array reference is a variable of type T, namely the variable within the array selected by the value of the
index expression.
JLS 15.14.1 -
A postfix expression followed by a ++ operator is a postfix increment expression. The result of the postfix expression
must be a variable of a numeric type, or a compile-time error occurs.

[This message has been edited by Nain Hwu (edited October 13, 2001).]