refactoring

src/com/bytezone/diskbrowser/visicalc/Count.java

@@ -18,7 +18,7 @@ public class Count
     for (Address address : range)
     {
       Cell cell = parent.getCell (address);
-      if (cell.hasValue () && cell.getValue () != 0.0)
+      if (cell != null && cell.hasValue () && cell.getValue () != 0.0)
         result += 1;
     }
 

src/com/bytezone/diskbrowser/visicalc/Sheet.java

@@ -18,7 +18,6 @@ public class Sheet implements Iterable<Cell>
   private final Map<Integer, Cell> sheet = new TreeMap<Integer, Cell> ();
   private final Map<String, Double> functions = new HashMap<String, Double> ();
 
-  final List<String> lines = new ArrayList<String> ();
   Cell currentCell = null;
   char defaultFormat;
 
@@ -138,11 +137,14 @@ public class Sheet implements Iterable<Cell>
       ;
 
     int ptr = 0;
-    while (ptr <= last)
+    final List<String> lines = new ArrayList<String> ();
+    while (ptr < last)
     {
-      int endPtr = findEndPtr (buffer, ptr);
-      add (HexFormatter.getString (buffer, ptr, endPtr - ptr));
-      ptr = endPtr + 1;
+      int length = getLineLength (buffer, ptr);
+      String line = HexFormatter.getString (buffer, ptr, length);
+      lines.add (line);
+      processLine (line);
+      ptr += length + 1;            // +1 for end-of-line token
     }
 
     if (true)
@@ -165,14 +167,15 @@ public class Sheet implements Iterable<Cell>
     }
   }
 
-  private int findEndPtr (byte[] buffer, int ptr)
+  private int getLineLength (byte[] buffer, int offset)
   {
-    while (buffer[ptr] != (byte) 0x8D)
+    int ptr = offset;
+    while (buffer[ptr] != (byte) 0x8D)        // end-of-line token
       ptr++;
-    return ptr;
+    return ptr - offset;
   }
 
-  private void add (String command)
+  private void processLine (String command)
   {
     // NB no closing bracket: [>K11:@SUM(J11...F11]
 
@@ -182,8 +185,6 @@ public class Sheet implements Iterable<Cell>
       return;
     }
 
-    lines.add (command);
-
     if (command.startsWith (">"))                               // GOTO cell
     {
       Matcher m = addressPattern.matcher (command);

src/com/bytezone/diskbrowser/visicalc/Sum.java

@@ -16,7 +16,11 @@ public class Sum
     double result = 0;
 
     for (Address address : range)
-      result += parent.getCell (address).getValue ();
+    {
+      Cell cell = parent.getCell (address);
+      if (cell != null && cell.hasValue ())
+        result += cell.getValue ();
+    }
 
     return result;
   }