Add toString() method on SevenZFile to display diagnostic information.
diff --git a/src/main/java/org/apache/commons/compress/archivers/sevenz/SevenZFile.java b/src/main/java/org/apache/commons/compress/archivers/sevenz/SevenZFile.java
index 809a9dc..90bda16 100644
--- a/src/main/java/org/apache/commons/compress/archivers/sevenz/SevenZFile.java
+++ b/src/main/java/org/apache/commons/compress/archivers/sevenz/SevenZFile.java
@@ -983,4 +983,9 @@
         }
         return skipped;
     }
+    
+    @Override
+    public String toString() {
+      return archive.toString();
+    }
 }