java replaceLast() [duplicate]

Question

Is there replaceLast() in Java? I saw there is replaceFirst().

EDIT: If there is not in the SDK, what would be a good implementation?

Answer 1

It could (of course) be done with regex:

public class Test {      public static String replaceLast(String text, String regex, String replacement) {         return text.replaceFirst("(?s)"+regex+"(?!.*?"+regex+")", replacement);     }      public static void main(String[] args) {         System.out.println(replaceLast("foo AB bar AB done", "AB", "--"));     } } 

although a bit cpu-cycle-hungry with the look-aheads, but that will only be an issue when working with very large strings (and many occurrences of the regex being searched for).

A short explanation (in case of the regex being AB):

(?s)     # enable dot-all option A        # match the character 'A' B        # match the character 'B' (?!      # start negative look ahead   .*?    #   match any character and repeat it zero or more times, reluctantly   A      #   match the character 'A'   B      #   match the character 'B' )        # end negative look ahead 

EDIT

Sorry to wake up an old post. But this is only for non-overlapping instances. For example .replaceLast("aaabbb", "bb", "xx"); returns "aaaxxb", not "aaabxx"

True, that could be fixed as follows:

public class Test {      public static String replaceLast(String text, String regex, String replacement) {         return text.replaceFirst("(?s)(.*)" + regex, "$1" + replacement);     }      public static void main(String[] args) {         System.out.println(replaceLast("aaabbb", "bb", "xx"));     } } 

Answer 2

If you don't need regex, here's a substring alternative.

public static String replaceLast(String string, String toReplace, String replacement) {     int pos = string.lastIndexOf(toReplace);     if (pos > -1) {         return string.substring(0, pos)              + replacement              + string.substring(pos + toReplace.length());     } else {         return string;     } } 

Testcase:

public static void main(String[] args) throws Exception {     System.out.println(replaceLast("foobarfoobar", "foo", "bar")); // foobarbarbar     System.out.println(replaceLast("foobarbarbar", "foo", "bar")); // barbarbarbar     System.out.println(replaceLast("foobarfoobar", "faa", "bar")); // foobarfoobar }