I am not sure I understand what you are saying here.

The way I understand String, is that a java string is composed of two
elements, the String object and its char sequence. When intern() is
called, the char sequence is shared between String objects, because
intern() returns a String object. So I thought intern() creates a new
String object which reuses the interned char sequence. But you are
saying it could return a pointer to itself. As a consequence of the
intern() call. Instead of creating a new String object, right? But how
does that save more memory than having two different pointers pointing
to the same String object, as in my seconds example? Both, what you are
saying, and what I am saying (through the second example) would then in
effect be the same, i.e. two pointers to the same object?

regards

Tommy

The problem with intern, is that interned strings live for the duration
of the system classloader (often the lifespan of the JVM instance),
which can lead to terrible memory leaks if used improperly.

It saves ram in the case where the same string may be duplicated.
An example where it wastes space is trivial to create.
public static void main(String...args) {
  for (int i = 0; i < Integer.MAX_VALUE; ++i) {
    System.out.println(("foo" + i).intern());
  }
}

Now, Integer.MAX_VALUE strings that will only appear once will be stored
indefinitely, leading to a memory leak, and probably an OOM on most
systems, where without the intern the program would run fine.

So, intern can save memory if you have many copies of the same string in
many places, but wastes memory if you don't.  The real moral is that
don't use intern unless you have a damned good reason to.  If you don't
know whether you're reason is good, then it probably isn't :-).

If you're getting OOM, and a memory profiler shows you that you have
millions of copies of "Foo1", *then* you should consider using intern.

Even then, consider other alternatives, such as a shorter lived String
pool so that you don't needlessly fill the intern pool.

(I have read your page on intern, but I could not find an answer to my
question.)

I understand that, but wouldn't a copy of the reference, as in
str2 = str1, save just as much memory as intern?

For example, say I have thousands of strings with the text
"http://www.sourceforge.org/", wouldn't having one copy of that String
in str1 and then for every other, just do strN = str1 save just as much
space as an intern? and do the job faster.

regards

Tommy