How to change a string in Set<String> during foreach iteration?

Question

I have a set of strings that I'd like to iterate over, and change all of those who equal something, to equal something else:

// Set<String> strings = new HashSet()
for (String str : strings) {
  if (str.equals("foo")) {
    // how do I change str to equal "bar"?
  }
}

I've tried replace() which didn't work. I've also tried removing "str" and adding the desired string, which caused an error. How would I go about doing this?

Answer 1

Two points:

1. String is immutable; you can't "change" a String. You can remove one from the Set and replace it with another, but that's all that changing.

2. A Set means "only one copy of each". What's the "change all" stuff? Why do you have to iterate over the Set? Why won't this do it?

   strings.remove("foo");
   strings.add("bar");

Answer 2

Since Set can't have duplicates, what you are trying to do is a bit strange. Why iterate?

if (strings.contains("foo")) {
  strings.remove("foo");
  strings.add("bar");
}

Make sure that whole block is synchronized properly if that strings set is shared between threads.