Consolidate duplicated col-index-to-string logic. Fixes issue #567

Author: rzymek

fastexcel-reader/src/main/java/org/dhatim/fastexcel/reader/CellAddress.java

@@ -100,14 +100,17 @@ public int hashCode() {
 
     @Override
     public String toString() {
-        StringBuilder sb = new StringBuilder();
-        format(sb, row, col);
-        return sb.toString();
+        return format(row, col).toString();
     }
 
-    static void format(StringBuilder sb, int row, int col) {
+    static StringBuilder format(int row, int col) {
+        return format(new StringBuilder(), row, col);
+    }
+
+    static StringBuilder format(StringBuilder sb, int row, int col) {
         sb.append(convertNumToColString(col));
         sb.append(row + 1);
+        return sb;
     }
 
     public static String convertNumToColString(int col) {

fastexcel-writer/src/main/java/org/dhatim/fastexcel/Cell.java

@@ -18,10 +18,11 @@
 import java.io.IOException;
 import java.time.LocalDate;
 import java.time.LocalDateTime;
-import java.time.ZoneId;
 import java.time.ZonedDateTime;
 import java.util.Date;
 
+import static org.dhatim.fastexcel.CellAddress.convertNumToColString;
+
 /**
  * A cell contains a value and a cached style index.
  */
@@ -47,7 +48,7 @@ class Cell implements Ref {
      */
     void write(Writer w, int r, int c) throws IOException {
         if (value != null || style != 0) {
-            w.append("<c r=\"").append(colToString(c)).append(r + 1).append('\"');
+            w.append("<c r=\"").append(convertNumToColString(c)).append(r + 1).append('\"');
             if (style != 0) {
                 w.append(" s=\"").append(style).append('\"');
             }

fastexcel-writer/src/main/java/org/dhatim/fastexcel/CellAddress.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright 2016 Dhatim.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.dhatim.fastexcel;
+
+import java.nio.charset.StandardCharsets;
+
+final class CellAddress {
+    private static final int COL_RADIX = 'Z' - 'A' + 1;
+
+    static StringBuilder format(int row, int col) {
+        return format(new StringBuilder(), row, col);
+    }
+
+    static StringBuilder format(StringBuilder sb, int row, int col) {
+        sb.append(convertNumToColString(col));
+        sb.append(row + 1);
+        return sb;
+    }
+
+    static String convertNumToColString(int col) {
+        // Excel counts column A as the 1st column, we
+        // treat it as the 0th one
+        int excelColNum = col + 1;
+
+        final int MAX_COL_CHARS = 3;
+        final byte[] colRef = new byte[MAX_COL_CHARS];
+        int colRemain = excelColNum;
+        int pos = 2;
+        while (colRemain > 0) {
+            int thisPart = colRemain % COL_RADIX;
+            if (thisPart == 0) {
+                thisPart = COL_RADIX;
+            }
+            colRemain = (colRemain - thisPart) / COL_RADIX;
+
+            colRef[pos--] = (byte) (thisPart + (int) 'A' - 1);
+        }
+        pos++;
+        return new String(colRef, pos, (MAX_COL_CHARS - pos), StandardCharsets.ISO_8859_1);
+    }
+}

fastexcel-writer/src/main/java/org/dhatim/fastexcel/Location.java

@@ -2,6 +2,8 @@
 
 import java.util.Comparator;
 
+import static org.dhatim.fastexcel.CellAddress.convertNumToColString;
+
 class Location implements Comparable<Location>, Ref {
     final int row;
     final int col;
@@ -28,7 +30,7 @@ public int compareTo(Location o) {
 
     @Override
     public String toString() {
-        return colToString(col) + (row + 1);
+        return convertNumToColString(col) + (row + 1);
     }
 
     @Override

fastexcel-writer/src/main/java/org/dhatim/fastexcel/Range.java

@@ -18,6 +18,8 @@
 import java.util.*;
 import java.util.stream.IntStream;
 
+import static org.dhatim.fastexcel.CellAddress.convertNumToColString;
+
 /**
  * Definition of a range of cells.
  */
@@ -139,7 +141,7 @@ public boolean equals(Object obj) {
 
     @Override
     public String toString() {
-        return colToString(left) + (top + 1) + ':' + colToString(right) + (bottom + 1);
+        return convertNumToColString(left) + (top + 1) + ':' + convertNumToColString(right) + (bottom + 1);
     }
 
     /**
@@ -150,7 +152,7 @@ public String toString() {
      * @return absolute reference
      */
     public String toAbsoluteString() {
-        return '$' + colToString(left) + '$' + (top + 1) + ":$" + colToString(right) + '$' + (bottom + 1);
+        return '$' + convertNumToColString(left) + '$' + (top + 1) + ":$" + convertNumToColString(right) + '$' + (bottom + 1);
     }
 
     /**

fastexcel-writer/src/main/java/org/dhatim/fastexcel/Ref.java

@@ -1,12 +1,4 @@
 package org.dhatim.fastexcel;
 
 public interface Ref {
-    default   String colToString(int col){
-        StringBuilder sb = new StringBuilder();
-        while (col >= 0) {
-            sb.append((char) ('A' + (col % 26)));
-            col = (col / 26) - 1;
-        }
-        return sb.reverse().toString();
-    }
 }

fastexcel-writer/src/main/java/org/dhatim/fastexcel/RepeatColRange.java

@@ -15,7 +15,9 @@
  */
 package org.dhatim.fastexcel;
 
-/** This class represents a range of columns for the 
+import static org.dhatim.fastexcel.CellAddress.convertNumToColString;
+
+/** This class represents a range of columns for the
  *      repeating columns feature in the print setup. */
 class RepeatColRange implements Ref {
 
@@ -32,6 +34,6 @@ public RepeatColRange(int from, int to) {
      */
     @Override
     public String toString() {
-        return "$" + colToString(from) + ":$" + colToString(to);
+        return "$" + convertNumToColString(from) + ":$" + convertNumToColString(to);
     }
 }

fastexcel-writer/src/main/java/org/dhatim/fastexcel/Worksheet.java

@@ -55,11 +55,6 @@ public class Worksheet implements Closeable {
      */
     public static final double MAX_ROW_HEIGHT = 409.5;
 
-    /**
-     * Helper for calculating column names
-     */
-    private static final Ref REF_HELPER = new Ref() {};
-
     private final Workbook workbook;
     private final String name;
     /**
@@ -860,12 +855,8 @@ private static void writeCol(Writer w, int columnIndex, double maxWidth, boolean
      * Helper method to get a cell name from (x, y) cell position.
      * e.g. "B3" from cell position (2, 1)
      */
-    static String getCellMark(int row, int coll) {
-        if (0 <= coll && coll <= 'Z' - 'A') {
-            char columnLetter = (char) ('A' + coll);
-            return String.valueOf(columnLetter) + String.valueOf(row+1);
-        }
-        return REF_HELPER.colToString(coll) + String.valueOf(row+1);
+    private static String getCellMark(int row, int col) {
+        return CellAddress.format(row,col).toString();
     }
 
 	@Override

fastexcel-writer/src/test/java/org/dhatim/fastexcel/CorrectnessTest.java

@@ -30,6 +30,7 @@
 import java.util.function.Consumer;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.dhatim.fastexcel.CellAddress.convertNumToColString;
 import static org.dhatim.fastexcel.Color.BLACK;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertThrows;
@@ -54,12 +55,9 @@ static byte[] writeWorkbook(Consumer<Workbook> consumer, String writeToFile) thr
 
     @Test
     void colToName() {
-        assertThat(new Ref() {
-        }.colToString(26)).isEqualTo("AA");
-        assertThat(new Ref() {
-        }.colToString(702)).isEqualTo("AAA");
-        assertThat(new Ref() {
-        }.colToString(Worksheet.MAX_COLS - 1)).isEqualTo("XFD");
+        assertThat(convertNumToColString(26)).isEqualTo("AA");
+        assertThat(convertNumToColString(702)).isEqualTo("AAA");
+        assertThat(convertNumToColString(Worksheet.MAX_COLS - 1)).isEqualTo("XFD");
     }
 
     @Test