Re: learning Java

["Luther Ananda Miller" <luther.miller@xxxxxxxxxx>]

> 1. String x = "100"; String y = "100"; if (x == y) {};
>      In this case I thought x would not equal y since they refer to
> different
>      objects and different memory locations. The book says that they do
>      match because the compiler re-uses the same String object if it sees
>      the contents match. Is this true only for String objects or other
> objects
>      treated the same way? Is this true for only String objects in the
same
>      class or does this optimization occur across classes?

I suppose this COULD be true for any class, but it is probably only true
since "100" is a static reference and the compiler can be easily written to
see this and take advantage of it. I don't there is any guarantee that the
same object will be used though so I wouldn't write code that depends on
this. Different compilers could produce different results..
You are best off in this case with if ( x.equals(y) ) { };
then you can always be sure of the result.

>  2. String x = "abc"; String y = "abc"; x  += "def";
>      I assume that after the first two statements, both x and y point to
the
>      same memory location. After the third statement, there are actually
>      two objects with different memory locations (x being "abcdef" and y
>      being "abc").

Yes- adding one string to another will create a new string object and then
in this case assign the new object to x.


+---
| This is the JAVA/400 Mailing List!
| To submit a new message, send your mail to JAVA400-L@midrange.com.
| To subscribe to this list send email to JAVA400-L-SUB@midrange.com.
| To unsubscribe from this list send email to JAVA400-L-UNSUB@midrange.com.
| Questions should be directed to the list owner: joe@zappie.net
+---