How to add prefix to each word in a given string

Question

I want to add prefix to every word in a given string. My code is :-

StringBuilder strColsToReturns  = new StringBuilder();
String strPrefix                = "abc.";
strColsToReturns.append(String.format(" %sId, %sname, %stype,", strPrefix, strPrefix, strPrefix));

This is fine, for small string, but I have a very large static string like this. So, this method of adding string prefix looks like a tedious method. Is there any other sophisticated way to achieve this.

Put each word in a `String[]` and then iterate over that list to prefix each element ? — Kewin Dousse, Aug 25 '16 at 08:21
Java 8 introduced the StringJoiner, where you can add a prefix.. looked at it ? — MrSimpleMind, Aug 25 '16 at 08:28
@MrSimpleMind but that prefix is added only before *first* element, not before *every* element. — Pshemo, Aug 25 '16 at 08:31

Pshemo · Accepted Answer · 2016-08-25T08:28:27.917

5

You can use replaceAll(regex, replacement). As regex we may want to select place which has

space or start of string before it
and non-space after it.

(we can use look-around mechanisms here)

So something like this should work:

String replaced = originalString.replaceAll("(?<=\\s|^)(?=\\S)", "abc.");

But if replacement can contain $ or \ characters you will need to escape them with \, or with Matcher.quoteReplacement(replacement) method.

String originalString = "foo bar baz";
String replaced = originalString.replaceAll("(?<=\\s|^)(?=\\S)", Matcher.quoteReplacement("abc."));
System.out.println(replaced);

Output: abc.foo abc.bar abc.baz

edited Aug 25 '16 at 08:28

answered Aug 25 '16 at 08:22

Pshemo

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I'd use a shorter `"(?<!\\S)(?=\\S)"` pattern. – Wiktor Stribiżew Aug 25 '16 at 08:32
@WiktorStribiżew Yes and +1 for this, but I will leave `(?<=\\s|^)` instead of `(?<!\\S)` since IMO it clearer shows what we are are after (negations may be more confusing). – Pshemo Aug 25 '16 at 08:34

How to add prefix to each word in a given string

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