Fix issue 4167

hutool-core/src/main/java/cn/hutool/core/text/split/SplitIter.java

@@ -71,29 +71,28 @@ protected String computeNext() {
 			return text.substring(offset);
 		}
 
-		final int start = finder.start(offset);
-		// 无分隔符，结束
-		if (start < 0) {
-			// 如果不再有分隔符，但是遗留了字符，则单独作为一个段
-			if (offset <= text.length()) {
-				final String result = text.substring(offset);
-				if (false == ignoreEmpty || false == result.isEmpty()) {
-					// 返回非空串
-					offset = Integer.MAX_VALUE;
-					return result;
+		String result = null;
+		int start;
+		do {
+			start = finder.start(offset);
+			// 无分隔符，结束
+			if (start < 0) {
+				// 如果不再有分隔符，但是遗留了字符，则单独作为一个段
+				if (offset <= text.length()) {
+					result = text.substring(offset);
+					if (!ignoreEmpty || !result.isEmpty()) {
+						// 返回非空串
+						offset = Integer.MAX_VALUE;
+						return result;
+					}
 				}
+				return null;
 			}
-			return null;
-		}
 
-		// 找到新的分隔符位置
-		final String result = text.substring(offset, start);
-		offset = finder.end(start);
-
-		if (ignoreEmpty && result.isEmpty()) {
-			// 发现空串且需要忽略时，跳过之
-			return computeNext();
-		}
+			// 找到新的分隔符位置
+			result = text.substring(offset, start);
+			offset = finder.end(start);
+		} while (ignoreEmpty && result.isEmpty()); // 空串则继续循环
 
 		count++;
 		return result;

hutool-core/src/main/java/cn/hutool/core/util/HexUtil.java

@@ -379,15 +379,24 @@ public static String format(final String hexStr) {
 	 * @return 格式化后的字符串
 	 */
 	public static String format(final String hexStr, String prefix) {
+		if (StrUtil.isEmpty(hexStr)) {
+			return StrUtil.EMPTY;
+		}
 		if (null == prefix) {
 			prefix = StrUtil.EMPTY;
 		}
 
 		final int length = hexStr.length();
 		final StringBuilder builder = StrUtil.builder(length + length / 2 + (length / 2 * prefix.length()));
-		builder.append(prefix).append(hexStr.charAt(0)).append(hexStr.charAt(1));
-		for (int i = 2; i < length - 1; i += 2) {
-			builder.append(CharUtil.SPACE).append(prefix).append(hexStr.charAt(i)).append(hexStr.charAt(i + 1));
+
+		for (int i = 0; i < length; i++) {
+			if (i % 2 == 0) {
+				if (i != 0) {
+					builder.append(CharUtil.SPACE);
+				}
+				builder.append(prefix);
+			}
+			builder.append(hexStr.charAt(i));
 		}
 		return builder.toString();
 	}

hutool-core/src/test/java/cn/hutool/core/text/split/SplitIterTest.java

@@ -6,6 +6,8 @@
 import cn.hutool.core.text.finder.StrFinder;
 import org.junit.jupiter.api.Test;
 
+import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 import java.util.regex.Pattern;
 
@@ -153,4 +155,18 @@ public void splitByEmptyTest(){
 			assertEquals(1, strings.size());
 		});
 	}
+
+	@Test
+	public void issue4169Test() {
+		StringBuilder sb = new StringBuilder();
+		for (int i = 0; i < 20000; i++) { // 1万次连续分隔符，模拟递归深度风险场景
+			sb.append(",");
+		}
+		sb.append("test");
+
+		SplitIter iter = new SplitIter(sb.toString(), new StrFinder(",",false), 0, true);
+		List<String> result = iter.toList(false);
+
+		assertEquals(Collections.singletonList("test"), result);
+	}
 }

hutool-core/src/test/java/cn/hutool/core/util/HexUtilTest.java

@@ -116,4 +116,35 @@ public void toBigIntegerTest() {
 		final String hex3 = "#FF";
 		assertEquals(new BigInteger("FF", 16), HexUtil.toBigInteger(hex3));
 	}
+
+	@Test
+	public void testFormatEmpty() {
+		String result = HexUtil.format("");
+		assertEquals("", result);
+	}
+
+	@Test
+	public void testFormatSingleChar() {
+		String result = HexUtil.format("1");
+		assertEquals("1", result);
+	}
+
+	@Test
+	public void testFormatOddLength() {
+		String result = HexUtil.format("123");
+		assertEquals("12 3", result);
+	}
+
+	@Test
+	public void testFormatWithPrefixSingleChar() {
+		String result = HexUtil.format("1", "0x");
+		assertEquals("0x1", result);
+	}
+
+	@Test
+	public void testFormatWithPrefixOddLength() {
+		String result = HexUtil.format("123", "0x");
+		assertEquals("0x12 0x3", result);
+	}
+
 }