Verson with StringBuffer doesn't work either:
public class smiec {
static StringBuffer a =new StringBuffer ("aaa");
static StringBuffer b = new StringBuffer ("bbb");
static void swap(StringBuffer x, StringBuffer y){
String temp = x.toString();
x =new StringBuffer ("jj");
y = null;
}
public static void main(String args[]) {
System.out.println("Before swap "
+ "a = " + a
+ " b = " + b);
swap(a, b);
System.out.println("After swap "
+ "a = " + a
+ " b = " + b);
}
}
-----Original Message-----
From: [email protected]
[mailto:[EMAIL PROTECTED] On Behalf Of Norman Ho
Sent: Friday, September 05, 2008 12:48 PM
To: Free Java Programming Online Training Course By Sang Shin
Subject: [java programming] Re: Passing parameters by reference question
Settting global variables doesn't work either, I just thought it would, but
I was wrong.
public class SwapString {
static String a = "aaa", b = "bbb";
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
System.out.println("Before swap "
+ "a = " + a
+ " b = " + b);
swap(a, b);
System.out.println("After swap "
+ "a = " + a
+ " b = " + b);
}
static void swap(String a, String b){
String temp = a;
a = b;
b = temp;
}
}
On Sep 5, 8:40 pm, miga <[EMAIL PROTECTED]> wrote:
> On Sep 5, 12:07 pm, Norman Ho <[EMAIL PROTECTED]> wrote:
>
>
>
> > I know this works:
>
> > public static void main(String[] args) {
>
> > String[] arr = {"aaa","bbb"};
> > int i = 0, j = 1;
> > System.out.println("Before swap "
> > + "arr[0] = " + arr[i]
> > + " arr[1] = " + arr[j]);
> > swap(arr, i, j);
> > System.out.println("After swap "
> > + "arr[0] = " + arr[i]
> > + " arr[1] = " + arr[j]);
> > }
>
> > static void swap(String[] arr, int i, int j){
> > String temp = arr[i];
> > arr[i] = arr[j];
> > arr[j] = temp;
> > }
>
> > But I don't understand why, they are both void.
>
> Because the array is known before sending it to the static method,
> therefore the swap works. In the method, you just change the internal
> values of the array, a bit as if you were using an int declared before
> the method, and changing it in the method; well, that's just an
> analogy.
>
> > If I go to the trouble of creating a class object with instance
> > variables, and a method swapString, would it have worked?
>
> Provided that you construct an array of those strings before the call
> to the swapString method, yes. Otherwise, static or not static, you
> will have the same trouble.
>
> The fact is you cannot return more than one thing from a method, so if
> you want to return two things, you have to create a collection of
> them, and work with that collection.- Hide quoted text -
>
> - Show quoted text -
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