Foreach can not manipulate a String list?

Question

I found this thread on the topic and I wondered why it's so hard in Java to replace a value in a List.

My code looks ugly like this:

    List<String> stringList = new ArrayList<>();
    // ... add some elements
    for (int i = 0; i< stringList.size(); ++i) {
        if (stringList.get(i).contains("%")) {
            stringList.set(i, stringList.get(i).replace("%", backupStorePath));
        }
    }

Is this really the only way to do this? Why can't I use a foreach loop?

for (String command : stringList) {
    command = command.replace("%", backupStorePath);
}

This must be a java's "Copy by value" problem and String being immutable, but why was it implemented like that? Why is command a copy of the original reference and not the original itself?

Answer 1

Since Java-8 you have a new option to use List.replaceAll:

stringList.replaceAll(command -> command.replace("%", backupStorePath));

Note that for loop works for any Iterable, not only List. And most of other iterables do not support the element replacement. So even if Java designers had decided to support modifications, it would be necessary to separate List and non-List cases which would certainly add some complexity.