JAL-629 improved comment and return speed of StringUtils.replaceLast()

diff --git a/src/jalview/util/StringUtils.java b/src/jalview/util/StringUtils.java
index 7e1b8ad..efaf3e2 100644 (file)
--- a/src/jalview/util/StringUtils.java
+++ b/src/jalview/util/StringUtils.java
@@ -600,6 +600,7 @@ public class StringUtils
 
   /*
    * implementation of String.replaceLast.
+   * Replaces only the last occurrence of toReplace in string with replacement.
    */
   public static String replaceLast(String string, String toReplace,
           String replacement)
@@ -607,8 +608,10 @@ public class StringUtils
     int pos = string.lastIndexOf(toReplace);
     if (pos > -1)
     {
-      return string.substring(0, pos) + replacement
-              + string.substring(pos + toReplace.length());
+      return new StringBuilder().append(string.substring(0, pos))
+              .append(replacement)
+              .append(string.substring(pos + toReplace.length()))
+              .toString();
     }
     else
     {