From 078ecacf6181f7e4cc87f9891e9f3a729025038a Mon Sep 17 00:00:00 2001
From: orbiter <orbiter@6c8d7289-2bf4-0310-a012-ef5d649a1542>
Date: Tue, 15 Mar 2011 00:47:30 +0000
Subject: [PATCH] avoid synchronization in DigestURI hash requests

git-svn-id: https://svn.berlios.de/svnroot/repos/yacy/trunk@7599 6c8d7289-2bf4-0310-a012-ef5d649a1542
---
 source/net/yacy/kelondro/data/meta/DigestURI.java | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/source/net/yacy/kelondro/data/meta/DigestURI.java b/source/net/yacy/kelondro/data/meta/DigestURI.java
index 4cae92a57..77002ab54 100644
--- a/source/net/yacy/kelondro/data/meta/DigestURI.java
+++ b/source/net/yacy/kelondro/data/meta/DigestURI.java
@@ -152,8 +152,11 @@ public class DigestURI extends MultiProtocolURI implements Serializable {
      */
     public final byte[] hash() {
         // in case that the object was initialized without a known url hash, compute it now
-        synchronized (this) {
-            if (this.hash == null) this.hash = urlHashComputation();
+        if (this.hash == null) {
+            // we check the this.hash value twice to avoid synchronization where possible
+            synchronized (this) {
+                if (this.hash == null) this.hash = urlHashComputation();
+            }
         }
         return this.hash;
     }