fix issue IDFMXJ，对stopWatch类中的stop方法计算出的耗时做 “非负校验”，确保耗时不会为负数。

hutool-core/src/main/java/cn/hutool/core/date/StopWatch.java

@@ -171,8 +171,9 @@ public class StopWatch {
 		}
 
 		final long lastTime = System.nanoTime() - this.startTimeNanos;
-		this.totalTimeNanos += lastTime;
-		this.lastTaskInfo = new TaskInfo(this.currentTaskName, lastTime);
+		final long safeLastTime = Math.max(0, lastTime);
+		this.totalTimeNanos += safeLastTime;
+		this.lastTaskInfo = new TaskInfo(this.currentTaskName, safeLastTime);
 		if (null != this.taskList) {
 			this.taskList.add(this.lastTaskInfo);
 		}

hutool-core/src/test/java/cn/hutool/core/date/IssueIDFMXJTest.java

@@ -0,0 +1,29 @@
+package cn.hutool.core.date;
+
+
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+import java.lang.reflect.Field;
+
+/**
+ * StopWatch 异常未释放资源问题测试（问题2）
+ */
+public class IssueIDFMXJTest {
+	@Test
+	void stopWatchNegativeTimeTest() throws NoSuchFieldException, IllegalAccessException {
+		final StopWatch stopWatch = new StopWatch();
+		stopWatch.start("负耗时测试任务");
+
+		// 反射修改startTimeNanos为当前时间+1秒（模拟nanoTime回退）
+		final Field startTimeNanosField = StopWatch.class.getDeclaredField("startTimeNanos");
+		startTimeNanosField.setAccessible(true);
+		startTimeNanosField.set(stopWatch, System.nanoTime() + 1_000_000_000);
+
+		stopWatch.stop();
+
+		Assertions.assertEquals(0, stopWatch.getLastTaskTimeNanos());
+		Assertions.assertEquals(0, stopWatch.getTotalTimeNanos());
+	}
+}