PDFBOX-5660: make field final, as suggested by Valery Bokov; closes #418

git-svn-id: https://svn.apache.org/repos/asf/pdfbox/trunk@1931785 13f79535-47bb-0310-9956-ffa450edef68

Author: THausherr

pdfbox/src/main/java/org/apache/pdfbox/pdfparser/XrefParser.java

@@ -52,7 +52,7 @@ public class XrefParser
      * Collects all Xref/trailer objects and resolves them into single
      * object using startxref reference. 
      */
-    private XrefTrailerResolver xrefTrailerResolver = new XrefTrailerResolver();
+    private final XrefTrailerResolver xrefTrailerResolver = new XrefTrailerResolver();
 
     private final COSParser parser;
     private final RandomAccessRead source;