optimize FillConfig initialization

easyexcel-core/src/main/java/com/alibaba/excel/write/executor/ExcelWriteFillExecutor.java

@@ -98,7 +98,7 @@ public class ExcelWriteFillExecutor extends AbstractExcelWriteExecutor {
         if (fillConfig == null) {
             fillConfig = FillConfig.builder().build();
         }
-        fillConfig.init();
+        // fillConfig.init();
 
         Object realData;
         // The data prefix that is populated this time

easyexcel-core/src/main/java/com/alibaba/excel/write/metadata/fill/FillConfig.java

@@ -21,37 +21,25 @@ import lombok.Setter;
 @NoArgsConstructor
 @AllArgsConstructor
 public class FillConfig {
-    private WriteDirectionEnum direction;
+
+    @Builder.Default
+    private WriteDirectionEnum direction = WriteDirectionEnum.VERTICAL;
+    
     /**
      * Create a new row each time you use the list parameter.The default create if necessary.
      * <p>
      * Warnning:If you use <code>forceNewRow</code> set true, will not be able to use asynchronous write file, simply
      * say the whole file will be stored in memory.
      */
-    private Boolean forceNewRow;
+    @Builder.Default
+    private Boolean forceNewRow = Boolean.FALSE;
 
     /**
      * Automatically inherit style
      *
      * default true.
      */
-    private Boolean autoStyle;
-
-    private boolean hasInit;
+    @Builder.Default
+    private Boolean autoStyle = Boolean.TRUE;
 
-    public void init() {
-        if (hasInit) {
-            return;
-        }
-        if (direction == null) {
-            direction = WriteDirectionEnum.VERTICAL;
-        }
-        if (forceNewRow == null) {
-            forceNewRow = Boolean.FALSE;
-        }
-        if (autoStyle == null) {
-            autoStyle = Boolean.TRUE;
-        }
-        hasInit = true;
-    }
 }

easyexcel-test/src/test/java/com/alibaba/easyexcel/test/core/fill/FillConfigTest.java

@@ -0,0 +1,49 @@
+package com.alibaba.easyexcel.test.core.fill;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.Test;
+
+import com.alibaba.excel.enums.WriteDirectionEnum;
+import com.alibaba.excel.write.metadata.fill.FillConfig;;
+
+public class FillConfigTest {
+
+    @Test
+    void creationByNewTest() {
+      // Non-arguments constructor
+      FillConfig config = new FillConfig();
+      assertEquals(config.getDirection(), WriteDirectionEnum.VERTICAL);
+      assertFalse(config.getForceNewRow());
+      assertTrue(config.getAutoStyle());
+
+      // Full-arguments constructor
+      config = new FillConfig(WriteDirectionEnum.HORIZONTAL, Boolean.TRUE, Boolean.FALSE);
+      assertEquals(config.getDirection(), WriteDirectionEnum.HORIZONTAL);
+      assertTrue(config.getForceNewRow());
+      assertFalse(config.getAutoStyle());
+    }
+
+    @Test
+    void creationByBuilderTest() {
+      // default builder
+      FillConfig config = FillConfig.builder().build();
+      assertEquals(config.getDirection(), WriteDirectionEnum.VERTICAL);
+      assertFalse(config.getForceNewRow());
+      assertTrue(config.getAutoStyle());
+
+      // builder with some actions
+      config = FillConfig.builder()
+        .direction(WriteDirectionEnum.HORIZONTAL)
+        .autoStyle(Boolean.FALSE)
+        .forceNewRow(Boolean.TRUE)
+        .build();
+      assertEquals(config.getDirection(), WriteDirectionEnum.HORIZONTAL);
+      assertTrue(config.getForceNewRow());
+      assertFalse(config.getAutoStyle());
+    }
+}