工具类加入私有构造方法

quickstart.md

@@ -1,5 +1,7 @@
 # easyexcel核心功能
 ## 目录
+### 前言
+读写的对象都用到了[Lombok](https://www.projectlombok.org/),他会自动生成`get`,`set` ，如果不需要自己创建对象并生成`get`,`set` 。
 ### 读
 DEMO代码地址：[https://github.com/alibaba/easyexcel/blob/master/src/test/java/com/alibaba/easyexcel/demo/read/ReadTest.java](/src/test/java/com/alibaba/easyexcel/test/demo/read/ReadTest.java)
 * [最简单的读](#simpleRead)

src/main/java/com/alibaba/excel/metadata/BasicParameter.java

@@ -1,6 +1,5 @@
 package com.alibaba.excel.metadata;
 
-import java.util.ArrayList;
 import java.util.List;
 
 import com.alibaba.excel.converters.Converter;
@@ -22,7 +21,7 @@ public class BasicParameter {
     /**
      * Custom type conversions override the default
      */
-    private List<Converter> customConverterList = new ArrayList<Converter>();
+    private List<Converter> customConverterList;
     /**
      * Automatic trim includes sheet name and content
      */

src/main/java/com/alibaba/excel/util/BooleanUtils.java

@@ -10,6 +10,8 @@ public class BooleanUtils {
     private static final String TRUE_NUMBER = "1";
     private static final String FALSE_NUMBER = "0";
 
+    private BooleanUtils() {}
+
     /**
      * String to boolean
      *

src/main/java/com/alibaba/excel/util/CollectionUtils.java

@@ -10,6 +10,8 @@ import java.util.Map;
  */
 public class CollectionUtils {
 
+    private CollectionUtils() {}
+
     public static boolean isEmpty(Collection<?> collection) {
         return (collection == null || collection.isEmpty());
     }

src/main/java/com/alibaba/excel/util/FileUtils.java

@@ -25,6 +25,8 @@ public class FileUtils {
     private static final String CACHE = "excache";
     private static final int WRITE_BUFF_SIZE = 8192;
 
+    private FileUtils() {}
+
     /**
      * Reads the contents of a file into a byte array. * The file is always closed.
      *

src/main/java/com/alibaba/excel/util/IoUtils.java

@@ -17,6 +17,8 @@ public class IoUtils {
      */
     private static final int DEFAULT_BUFFER_SIZE = 1024 * 4;
 
+    private IoUtils() {}
+
     /**
      * Gets the contents of an InputStream as a byte[].
      *

src/main/java/com/alibaba/excel/util/PositionUtils.java

@@ -5,6 +5,8 @@ package com.alibaba.excel.util;
  */
 public class PositionUtils {
 
+    private PositionUtils() {}
+
     public static int getRow(String currentCellIndex) {
         int row = 0;
         if (currentCellIndex != null) {

src/main/java/com/alibaba/excel/util/StringUtils.java

@@ -7,6 +7,8 @@ package com.alibaba.excel.util;
  */
 public class StringUtils {
 
+    private StringUtils() {}
+
     public static boolean isEmpty(Object str) {
         return (str == null || "".equals(str));
     }

src/main/java/com/alibaba/excel/util/StyleUtil.java

@@ -17,6 +17,8 @@ import com.alibaba.excel.write.metadata.style.WriteFont;
  */
 public class StyleUtil {
 
+    private StyleUtil() {}
+
     /**
      * @param workbook
      * @return

src/main/java/com/alibaba/excel/util/WorkBookUtil.java

@@ -22,6 +22,8 @@ import com.alibaba.excel.write.metadata.holder.WriteWorkbookHolder;
  */
 public class WorkBookUtil {
 
+    private WorkBookUtil() {}
+
     public static Workbook createWorkBook(WriteWorkbookHolder writeWorkbookHolder)
         throws IOException, InvalidFormatException {
         if (ExcelTypeEnum.XLSX.equals(writeWorkbookHolder.getExcelType())) {