diff --git a/hutool-core/src/test/java/cn/hutool/core/lang/hash/MetroHashTest.java b/hutool-core/src/test/java/cn/hutool/core/lang/hash/MetroHashTest.java
index 58b31fe3d..5577a1bb5 100644
--- a/hutool-core/src/test/java/cn/hutool/core/lang/hash/MetroHashTest.java
+++ b/hutool-core/src/test/java/cn/hutool/core/lang/hash/MetroHashTest.java
@@ -3,13 +3,12 @@ package cn.hutool.core.lang.hash;
 
 import cn.hutool.core.util.CharsetUtil;
 import cn.hutool.core.util.HexUtil;
+import cn.hutool.core.util.RandomUtil;
 import cn.hutool.core.util.StrUtil;
 import org.junit.Assert;
 import org.junit.Ignore;
 import org.junit.Test;
 
-import java.util.Random;
-
 /**
  * https://gitee.com/dromara/hutool/pulls/532
  */
@@ -41,7 +40,7 @@ public class MetroHashTest {
 	@Test
 	@Ignore
 	public void bulkHashing64Test() {
-		String[] strArray = getRandomStringArray(10000000);
+		String[] strArray = getRandomStringArray();
 		long startCity = System.currentTimeMillis();
 		for (String s : strArray) {
 			CityHash.hash64(s.getBytes());
@@ -65,7 +64,7 @@ public class MetroHashTest {
 	@Test
 	@Ignore
 	public void bulkHashing128Test() {
-		String[] strArray = getRandomStringArray(10000000);
+		String[] strArray = getRandomStringArray();
 		long startCity = System.currentTimeMillis();
 		for (String s : strArray) {
 			CityHash.hash128(s.getBytes());
@@ -83,26 +82,12 @@ public class MetroHashTest {
 	}
 
 
-	private static String[] getRandomStringArray(int length) {
-		String[] result = new String[length];
-		Random random = new Random();
+	private static String[] getRandomStringArray() {
+		String[] result = new String[10000000];
 		int index = 0;
-		while (index < length) {
-			result[index++] = getRandomString(random.nextInt(64));
+		while (index < 10000000) {
+			result[index++] = RandomUtil.randomString(RandomUtil.randomInt(64));
 		}
 		return result;
 	}
-
-	private static String getRandomString(int length) {
-		String str = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
-		Random random = new Random();
-		StringBuffer sb = new StringBuffer();
-		for (int i = 0; i < length; i++) {
-			int number = random.nextInt(62);
-			sb.append(str.charAt(number));
-		}
-		return sb.toString();
-	}
-
-
 }
diff --git a/hutool-json/src/main/java/cn/hutool/json/JSONObject.java b/hutool-json/src/main/java/cn/hutool/json/JSONObject.java
index a7582edd4..6442d84c7 100644
--- a/hutool-json/src/main/java/cn/hutool/json/JSONObject.java
+++ b/hutool-json/src/main/java/cn/hutool/json/JSONObject.java
@@ -592,9 +592,14 @@ public class JSONObject implements JSON, JSONGetter<String>, Map<String, Object>
 		final JSONWriter jsonWriter = JSONWriter.of(writer, indentFactor, indent, config)
 				.beginObj();
 		this.forEach((key, value) -> {
-			final MutablePair<String, Object> pair = new MutablePair<>(key, value);
-			if (null == filter || filter.accept(pair)) {
-				jsonWriter.writeField(pair.getKey(), pair.getValue());
+			if (null != filter){
+				final MutablePair<String, Object> pair = new MutablePair<>(key, value);
+				if (filter.accept(pair)) {
+					// 使用修改后的键值对
+					jsonWriter.writeField(pair.getKey(), pair.getValue());
+				}
+			} else {
+				jsonWriter.writeField(key, value);
 			}
 		});
 		jsonWriter.end();
diff --git a/hutool-json/src/test/java/cn/hutool/json/JSONObjectTest.java b/hutool-json/src/test/java/cn/hutool/json/JSONObjectTest.java
index 3b18c8059..afa1616f0 100644
--- a/hutool-json/src/test/java/cn/hutool/json/JSONObjectTest.java
+++ b/hutool-json/src/test/java/cn/hutool/json/JSONObjectTest.java
@@ -30,7 +30,6 @@ import org.junit.Test;
 
 import java.math.BigDecimal;
 import java.sql.Timestamp;
-import java.time.LocalDate;
 import java.util.Date;
 import java.util.HashMap;
 import java.util.List;
@@ -658,6 +657,21 @@ public class JSONObjectTest {
 		Assert.assertEquals("{\"b\":\"value2_edit\"}", s);
 	}
 
+	@Test
+	public void toUnderLineCaseTest() {
+		JSONObject json1 = JSONUtil.createObj(JSONConfig.create().setOrder(true))
+				.set("aKey", "value1")
+				.set("bJob", "value2")
+				.set("cGood", "value3")
+				.set("d", true);
+
+		final String s = json1.toJSONString(0, (pair) -> {
+			pair.setKey(StrUtil.toUnderlineCase(pair.getKey()));
+			return true;
+		});
+		Assert.assertEquals("{\"a_key\":\"value1\",\"b_job\":\"value2\",\"c_good\":\"value3\",\"d\":true}", s);
+	}
+
 	@Test
 	public void nullToEmptyTest() {
 		JSONObject json1 = JSONUtil.createObj(JSONConfig.create().setOrder(true).setIgnoreNullValue(false))