cannot change strings?

In the Exam Cram book, Chapter 3 states that Strings cannot be changed once initialized. Huh?!!! I do not understand this...
If I run and compile this:
String s = "This string";
s = "That string";
System.out.println(s);
My machine spits out That string when run. Am I not changing the string?? Please help. Thanks!!!

Hi Barry,
String types are really object references. They hold a reference to the place in memory where the string is stored.
When you enter <code>s = "That String"</code> the compiler actually replaces it with <code>s = new String("That string")</code> and returns an object reference the new string.
So, while it looks as if you've changed the string what's actually happened is that a new string object was created.
Hope that helps.
PS There is one exception to the above. Java maintains a string pool. Every time you create a string without explicitly using new or concatenating two strings; the compiler puts them in a memory pool. It checks there first to see if the string you're trying to create already exists; if it does it will return an object reference to the string in the pool; otherwise it creates a new string.

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Jane

Ok, I suppose I understand this now. It is kind of strange to think of it that way though. Thanks for the info!