[github-582] improve performance CodepointsUtil.iteratorFor. Thanks to Jason Mirra. This closes #582

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1915572 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 12 insertions, 3 deletions

diff --git a/poi/src/main/java/org/apache/poi/util/CodepointsUtil.java b/poi/src/main/java/org/apache/poi/util/CodepointsUtil.java
index b74cf8a88c..732af2e3ff 100644
--- a/poi/src/main/java/org/apache/poi/util/CodepointsUtil.java
+++ b/poi/src/main/java/org/apache/poi/util/CodepointsUtil.java
@@ -29,9 +29,18 @@ public class CodepointsUtil {
      * @see #primitiveIterator(String) a more performant iterator
      */
     public static Iterator<String> iteratorFor(String text) {
-        return text.codePoints()
-                .mapToObj(codePoint -> new String(Character.toChars(codePoint)))
-                .iterator();
+        final PrimitiveIterator.OfInt iter = primitiveIterator(text);
+        return new Iterator<String>() {
+            @Override
+            public boolean hasNext() {
+                return iter.hasNext();
+            }
+
+            @Override
+            public String next() {
+                return new String(Character.toChars(iter.nextInt()));
+            }
+        };
     }
 
     /**