From ca89b25c8fd28e70d912614650151528aa0c545c Tue, 31 Mar 2015 15:44:50 +0300
From: Robert Munteanu <rmuntean@adobe.com>
Date: Tue, 31 Mar 2015 15:40:35 +0300
Subject: [PATCH] OAK-2710 - Utils.unshareString should not generate String instances unless needed 

diff --git a/oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/document/util/Utils.java b/oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/document/util/Utils.java
index c40f359..ce9c135 100644
--- a/oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/document/util/Utils.java
+++ b/oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/document/util/Utils.java
@@ -35,6 +35,7 @@
 import javax.annotation.Nullable;
 
 import com.google.common.base.Predicate;
+import com.google.common.base.StandardSystemProperty;
 import com.google.common.collect.AbstractIterator;
 import com.mongodb.BasicDBObject;
 
@@ -57,6 +58,32 @@
  * Utility methods.
  */
 public class Utils {
+
+    private static final boolean NEEDS_STRING_UNSHARE;
+
+    static {
+        String version = System.getProperty(StandardSystemProperty.JAVA_VERSION.key());
+
+        if (version.startsWith("1.6")) {
+            // always unshare for Java 1.6
+            NEEDS_STRING_UNSHARE = true;
+        } else if (version.startsWith("1.7")) {
+            // unshare for 1.7 if we have an old enough version
+            int buildSeparatorIdx = version.indexOf('_');
+            if (buildSeparatorIdx != -1 && buildSeparatorIdx < version.length()) {
+                int build = Integer.parseInt(version.substring(buildSeparatorIdx + 1));
+                NEEDS_STRING_UNSHARE = build < 6;
+            } else {
+                // if we can't parse the build number, fall back to unsharing
+                NEEDS_STRING_UNSHARE = true;
+            }
+
+        } else {
+            // none of the versions following 1.7 need unsharing
+            NEEDS_STRING_UNSHARE = false;
+        }
+    }
+
     private static final Logger LOG = LoggerFactory.getLogger(Utils.class);
 
     /**
@@ -105,10 +132,14 @@
      * http://mail.openjdk.java.net/pipermail/core-libs-dev/2012-May/010257.html
      *
      * @param x the string
-     * @return the new string
+     * @return the new string or the passed string for recent enough versions of Java 
      */
     public static String unshareString(String x) {
-        return new String(x);
+        if (NEEDS_STRING_UNSHARE) {
+            return new String(x);
+        }
+
+        return x;
     }
 
     public static int pathDepth(String path) {