修复StrBuilderinsert插入计算错误问题（issue#ICTSRZ@Gitee）

CHANGELOG.md

@@ -2,7 +2,7 @@
 # 🚀Changelog
 
 -------------------------------------------------------------------------------------------------------------
-# 5.8.40(2025-08-19)
+# 5.8.40(2025-08-20)
 
 ### 🐣新特性
 * 【captcha】      `MathGenerator`四则运算方式支持不生成负数结果（pr#1363@Gitee）
@@ -19,6 +19,7 @@
 * 【core   】      修复`ChineseDate `闰年闰月节日获取问题（issue#ICL1BT@Gitee）
 * 【core   】      修复`TreeBuilder`append重复向idTreeMap中put问题（pr#3992@Github）
 * 【extra  】      修复`QLExpressEngine`allowClassSet无效问题（issue#3994@Github）
+* 【core   】      修复`StrBuilder`insert插入计算错误问题（issue#ICTSRZ@Gitee）
 
 -------------------------------------------------------------------------------------------------------------
 # 5.8.39(2025-06-20)

hutool-core/src/main/java/cn/hutool/core/text/StrBuilder.java

@@ -271,7 +271,7 @@ public class StrBuilder implements CharSequence, Appendable, Serializable {
 		} else if (csq instanceof StrBuilder) {
 			((StrBuilder) csq).getChars(0, len, this.value, index);
 		} else {
-			for (int i = 0, j = this.position; i < len; i++, j++) {
+			for (int i = 0, j = index; i < len; i++, j++) {
 				this.value[j] = csq.charAt(i);
 			}
 		}
@@ -316,7 +316,7 @@ public class StrBuilder implements CharSequence, Appendable, Serializable {
 
 		final int length = end - start;
 		moveDataAfterIndex(index, length);
-		for (int i = start, j = this.position; i < end; i++, j++) {
+		for (int i = start, j = index; i < end; i++, j++) {
 			value[j] = csq.charAt(i);
 		}
 		this.position = Math.max(this.position, index) + length;

hutool-core/src/test/java/cn/hutool/core/text/StrBuilderTest.java

@@ -1,12 +1,13 @@
 package cn.hutool.core.text;
 
-import static org.junit.jupiter.api.Assertions.*;
-import org.junit.jupiter.api.Disabled;
-import org.junit.jupiter.api.Test;
-
 import cn.hutool.core.date.DateUtil;
 import cn.hutool.core.date.TimeInterval;
 import cn.hutool.core.lang.Console;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
 
 /**
  * StrBuilder单元测试
@@ -116,4 +117,18 @@ public class StrBuilderTest {
 		builder = strBuilder.delTo(0);
 		assertEquals("", builder.toString());
 	}
+
+	@Test
+	void issueICTSRZTest() {
+		final StrBuilder helloWorld = StrBuilder.create("Hello World");
+		helloWorld.insert(6, "Beautiful ", 0, 10);
+		Assertions.assertEquals("Hello Beautiful World", helloWorld.toString());
+	}
+
+	@Test
+	void issueICTSRZTest2() {
+		final StrBuilder helloWorld = StrBuilder.create("Hello World");
+		helloWorld.insert(6, "Beautiful ");
+		Assertions.assertEquals("Hello Beautiful World", helloWorld.toString());
+	}
 }