learning Java

I have been spending a lot of time lately learning Java, but have run
across a couple of things I don't understand. My background is RPG
and I don't know C or C++.

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?

 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").

Joe Teff

+---
| 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
+---