String reference remains same during clone()

[Vijay Raj]

import static java.lang.System.out;
 
public class CloneTest implements Cloneable
{
private int count;
private String str;
 
CloneTest()
{
count = 10;
str = new String("hello");
}
 
public static void main(String[] args) throws CloneNotSupportedException
{
CloneTest ct = new CloneTest();
ct.test(ct.clone());
out.println(ct.count);
out.println(ct.str);
}
 
private void test(Object obj)
{
CloneTest ct1 = (CloneTest)obj;
ct1.count = 20;
ct1.str = new String("again_hello");
}
}

In the above code, I have two instance variables, one a primitive type and another a String variable. After calling test(), the integer variable remains the same as expected. But the String reference also remains the same (prints "hello"). Shouldn't the modification made in the method test() be reflected, i.e., it should have printed "again_hello" instead of "hello". This is what shallow copying is, right?

regards,
vijay.

[Ko Wey]

 
private void test(Object obj)
{
CloneTest ct1 = (CloneTest)obj;
ct1.count = 20;
ct1.str = new String("again_hello");
} 

CloneTest ct1 is declared and initialized within method: test(Object obj)
so after leaving this method ct1 (and its string str) do not exist anymore.
Isn't this thinking correct?

[Bimal Patel]

Hi,

private void test(Object obj)
{
CloneTest ct1 = (CloneTest)obj;
ct1.count = 20;
ct1.str = new String("again_hello");
}

[/qb]<hr></blockquote>

Can you try as below:

private void test(CloneTest obj)
{
obj.count = 20;
obj.str = new String("again_hello");
}

Just a wild guess
[ November 12, 2005: Message edited by: Bimal Patel ]

[Marilyn de Queiroz]

Vijay R.
I am sorry to inform you that a last initial is not the same as a last name. The JavaRanch Name Policy requires a first name, a space, and a last name. You can change it here.

[Vijay Raj]

Ko Wey:
But we are referencing the same string object, so change made in test() should reflect back.

Bimal Patel:
Tried making a call to test() from main() as

 ct.test((CloneTest)ct.clone()) 

but to no avail. It still prints "hello".

regards,
vijay.

[Ko Wey]

CloneTest ct = new CloneTest();
ct.test(ct.clone());
out.println(ct.count);
out.println(ct.str);

In ct.test(ct.clone()) I make a copy (ct.clone()),
I then change the copy (test(ct.clone))
an then I look at the original's members, not those of the copy!

If I change the code to this:

CloneTest ct = new CloneTest();
CloneTest ctx = (CloneTest)ct.clone();
ct.test(ctx);
 
System.out.println("ct:"+ct.count);
System.out.println("ct:"+ct.str);
System.out.println("ctx:"+ctx.count);
System.out.println("ctx:"+ctx.str);

I get this print-out:
ct:10
ct:hello
ctx:20
ctx:again_hello

which is what was wanted, yes?