Android: How to convert a list of strings or objects to a single string

Android FAQ: How do I convert a list of strings (or a list of objects) to a single, combined string?

In Android, if you want to convert a list of strings to a String, I just saw this approach:

List<String> list = new ArrayList<String>();
list.add("foo");
list.add("bar");
list.add("baz");
String joined = TextUtils.join(", ", list);

That approach works great if you happen to have a List<String>, but if you want to convert a list of objects to a String, I think you’ll have to use the old-fashioned approach:

StringBuilder sb = new StringBuilder();
int count = 1;
for (User u: users) {
    sb.append("" + count++ + ": " + u.firstName + " " + u.lastName + "\n");
}
mEditText.setText(sb.toString());

As shown, I use that approach to convert a list of users to a list of custom strings.

There may be other ways to approach this as Android adopts Java 8 standards, but for now, these examples show the best ways I know to convert a list of strings and a list of custom objects to a single string.