diff --git a/net/src/main/java/com/zfoo/net/packet/PacketService.java b/net/src/main/java/com/zfoo/net/packet/PacketService.java
index 92425091..4d575416 100644
--- a/net/src/main/java/com/zfoo/net/packet/PacketService.java
+++ b/net/src/main/java/com/zfoo/net/packet/PacketService.java
@@ -27,7 +27,7 @@ import com.zfoo.protocol.serializer.CodeLanguage;
 import com.zfoo.protocol.util.DomUtils;
 import com.zfoo.protocol.util.StringUtils;
 import com.zfoo.protocol.xml.XmlProtocols;
-import com.zfoo.util.math.NumberUtils;
+import com.zfoo.protocol.util.NumberUtils;
 import io.netty.buffer.ByteBuf;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
diff --git a/protocol/src/main/java/com/zfoo/protocol/collection/CollectionUtils.java b/protocol/src/main/java/com/zfoo/protocol/collection/CollectionUtils.java
index 99e1272d..8719f478 100644
--- a/protocol/src/main/java/com/zfoo/protocol/collection/CollectionUtils.java
+++ b/protocol/src/main/java/com/zfoo/protocol/collection/CollectionUtils.java
@@ -13,7 +13,6 @@
 package com.zfoo.protocol.collection;
 
 
-import com.zfoo.protocol.collection.model.NaturalComparator;
 import com.zfoo.protocol.model.Pair;
 import com.zfoo.protocol.util.AssertionUtils;
 import com.zfoo.protocol.util.IOUtils;
@@ -131,11 +130,11 @@ public abstract class CollectionUtils {
      * @return a new sorted List, containing the elements of Collection a and b
      */
     public static <T extends Comparable<? super T>> List<T> collate(List<? extends T> aList, List<? extends T> bList) {
-        return collate(aList, bList, NaturalComparator.getInstance(), true);
+        return collate(aList, bList, Comparator.naturalOrder(), true);
     }
 
     public static <T extends Comparable<? super T>> List<T> collate(List<? extends T> aList, List<? extends T> bList, boolean includeDuplicates) {
-        return collate(aList, bList, NaturalComparator.getInstance(), includeDuplicates);
+        return collate(aList, bList, Comparator.naturalOrder(), includeDuplicates);
     }
 
     public static <T> List<T> collate(List<T> aList, List<T> bList, Comparator<T> comparator) {
diff --git a/protocol/src/main/java/com/zfoo/protocol/collection/model/NaturalComparator.java b/protocol/src/main/java/com/zfoo/protocol/collection/model/NaturalComparator.java
deleted file mode 100644
index 7a00100a..00000000
--- a/protocol/src/main/java/com/zfoo/protocol/collection/model/NaturalComparator.java
+++ /dev/null
@@ -1,72 +0,0 @@
-/*
- * Copyright (C) 2020 The zfoo Authors
- * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
- * in compliance with the License. You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed
- * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and limitations under the License.
- */
-
-package com.zfoo.protocol.collection.model;
-
-import java.util.Comparator;
-
-public class NaturalComparator<E extends Comparable<? super E>> implements Comparator<E> {
-
-
-    /**
-     * The singleton instance.
-     */
-    private static final NaturalComparator<?> INSTANCE = new NaturalComparator<>();
-
-    //-----------------------------------------------------------------------
-
-    /**
-     * Constructor whose use should be avoided.
-     * <p>
-     * Please use the {@link #getInstance()} method whenever possible.
-     */
-    public NaturalComparator() {
-        super();
-    }
-
-    //-----------------------------------------------------------------------
-
-    /**
-     * Gets the singleton instance of a ComparableComparator.
-     * <p>
-     * Developers are encouraged to use the comparator returned from this method
-     * instead of constructing a new instance to reduce allocation and GC overhead
-     * when multiple comparable comparators may be used in the same VM.
-     *
-     * @param <E> the element type
-     * @return the singleton ComparableComparator
-     */
-    public static <E extends Comparable<? super E>> NaturalComparator<E> getInstance() {
-        return (NaturalComparator<E>) INSTANCE;
-    }
-
-    //-----------------------------------------------------------------------
-
-    /**
-     * Compare the two {@link Comparable Comparable} arguments.
-     * This method is equivalent to:
-     * <pre>((Comparable)obj1).compareTo(obj2)</pre>
-     *
-     * @param a the first object to compare
-     * @param b the second object to compare
-     * @return negative if obj1 is less, positive if greater, zero if equal
-     * @throws NullPointerException if <i>obj1</i> is <code>null</code>,
-     *                              or when <code>((Comparable)obj1).compareTo(obj2)</code> does
-     * @throws ClassCastException   if <i>obj1</i> is not a <code>Comparable</code>,
-     *                              or when <code>((Comparable)obj1).compareTo(obj2)</code> does
-     */
-    @Override
-    public int compare(final E a, final E b) {
-        return a.compareTo(b);
-    }
-
-}
diff --git a/util/src/main/java/com/zfoo/util/math/NumberUtils.java b/protocol/src/main/java/com/zfoo/protocol/util/NumberUtils.java
similarity index 99%
rename from util/src/main/java/com/zfoo/util/math/NumberUtils.java
rename to protocol/src/main/java/com/zfoo/protocol/util/NumberUtils.java
index 0c052e23..de495fac 100644
--- a/util/src/main/java/com/zfoo/util/math/NumberUtils.java
+++ b/protocol/src/main/java/com/zfoo/protocol/util/NumberUtils.java
@@ -1,6 +1,5 @@
 /*
  * Copyright (C) 2020 The zfoo Authors
- *
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
  * in compliance with the License. You may obtain a copy of the License at
  *
@@ -11,11 +10,9 @@
  * See the License for the specific language governing permissions and limitations under the License.
  */
 
-package com.zfoo.util.math;
+package com.zfoo.protocol.util;
 
 import com.zfoo.protocol.collection.ArrayUtils;
-import com.zfoo.protocol.util.AssertionUtils;
-import com.zfoo.protocol.util.StringUtils;
 
 import java.math.BigDecimal;
 import java.math.RoundingMode;
diff --git a/util/src/main/java/com/zfoo/util/math/RandomUtils.java b/util/src/main/java/com/zfoo/util/math/RandomUtils.java
index 994b7e27..ceb0d8b4 100644
--- a/util/src/main/java/com/zfoo/util/math/RandomUtils.java
+++ b/util/src/main/java/com/zfoo/util/math/RandomUtils.java
@@ -13,6 +13,7 @@
 
 package com.zfoo.util.math;
 
+import com.zfoo.protocol.util.NumberUtils;
 import com.zfoo.protocol.util.StringUtils;
 
 import java.math.BigDecimal;