don't create a new buffer for each loop iteration

core/src/main/java/hudson/Util.java

@@ -521,9 +521,10 @@ public class Util {
         try {
             MessageDigest md5 = MessageDigest.getInstance("MD5");
 
+            byte[] buffer = new byte[1024];
             DigestInputStream in =new DigestInputStream(source,md5);
             try {
-                while(in.read(new byte[1024])>0)
+                while(in.read(buffer)>0)
                     ; // simply discard the input
             } finally {
                 in.close();