diff --git a/src/main/java/util/StringHelper.java b/src/main/java/util/StringHelper.java
index 60b9c73..0599da2 100644
--- a/src/main/java/util/StringHelper.java
+++ b/src/main/java/util/StringHelper.java
@@ -4,6 +4,7 @@ import java.nio.ByteBuffer;
 import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.LinkedList;
+import java.util.List;
 
 /*
  * @Author: Wang Feng
@@ -12,7 +13,45 @@ import java.util.LinkedList;
  * @Date: 11:27 2021/3/10
  * @Copyright: MIN-Group；国家重大科技基础设施——未来网络北大实验室；深圳市信息论与未来网络重点实验室
  */
+class VarByteArray{
+    private int MaxNum=9000; // byte初始化长度
+    private byte[] bytes;
+    private int len;  //实际长度
+    public VarByteArray(){
+        bytes=new byte[MaxNum];
+        len=0;
+    }
+    public VarByteArray(int maxNum){
+        MaxNum=maxNum;
+        bytes=new byte[MaxNum];
+        len=0;
+    }
 
+    /**
+     * put进一个byte
+     * @param b
+     */
+    public void put(byte b){
+        while(len>=MaxNum) {
+            MaxNum*=2;
+            byte[] newBytes=new byte[MaxNum];
+            System.arraycopy(bytes,0,newBytes,0,len);
+            bytes=newBytes;
+        }
+        bytes[len] = b;
+        len++;
+    }
+
+    /**
+     * 返回一个byte[]
+     * @return
+     */
+    public byte[] byteArray(){
+        byte[] res=new byte[len];
+        System.arraycopy(bytes,0,res,0,len);
+        return res;
+    }
+}
 public class StringHelper {
 
     private static byte toHexChar(byte n){
@@ -50,26 +89,26 @@ public class StringHelper {
     public static String escape(String str){
         byte[] strBytes=str.getBytes(StandardCharsets.UTF_8);
         int len=strBytes.length;
-        ByteBuffer byteBuffer = null;
-        int index=0;
+        VarByteArray byteBuffer = new VarByteArray(str.getBytes().length);
+//        int index=0;
         for(int i=0;i<len;i++){
             byte ch=strBytes[i];
             if((ch>='a'&&ch<='z')||
                     (ch>='A'&&ch<='Z')||
                     (ch>='0'&&ch<='9')||
                     ch=='-'||ch=='.'||ch=='_'||ch=='~'){
-                byteBuffer.put(index,ch);
-                index++;
+                byteBuffer.put(ch);
+//                index++;
             }else{
-                byteBuffer.put(index,(byte)'%');
-                index++;
-                byteBuffer.put(index,toHexChar((byte) ((ch & 0xf0) >> 4)));
-                index++;
-                byteBuffer.put(index,toHexChar((byte) (ch & 0xf)));
-                index++;
+                byteBuffer.put((byte)'%');
+//                index++;
+                byteBuffer.put(toHexChar((byte) ((ch & 0xf0) >> 4)));
+//                index++;
+                byteBuffer.put(toHexChar((byte) (ch & 0xf)));
+//                index++;
             }
         }
-        return new String(byteBuffer.array());
+        return new String(byteBuffer.byteArray());
     }
 
     /**
diff --git a/src/test/java/encoding/TestSizeT.java b/src/test/java/encoding/SizeTest.java
similarity index 97%
rename from src/test/java/encoding/TestSizeT.java
rename to src/test/java/encoding/SizeTest.java
index e0ed0de..7a59e11 100644
--- a/src/test/java/encoding/TestSizeT.java
+++ b/src/test/java/encoding/SizeTest.java
@@ -12,7 +12,7 @@ import java.math.BigInteger;
  * @Date: 21:27 2021/03/02
  * @Copyright: MIN-Group；国家重大科技基础设施——未来网络北大实验室；深圳市信息论与未来网络重点实验室
  */
-public class TestSizeT {
+public class SizeTest {
 
     public static void main(String[] args){
 //        BigInteger bigInteger=new BigInteger("3");
diff --git a/src/test/java/util/StringHelperTest.java b/src/test/java/util/StringHelperTest.java
new file mode 100644
index 0000000..ca51155
--- /dev/null
+++ b/src/test/java/util/StringHelperTest.java
@@ -0,0 +1,44 @@
+package util;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+/*
+ * @Author: Wang Feng
+ * @Description:
+ * @Version: 1.0.0
+ * @Date: 19:47 2021/3/23
+ * @Copyright: MIN-Group；国家重大科技基础设施——未来网络北大实验室；深圳市信息论与未来网络重点实验室
+ */
+public class StringHelperTest {
+    @Test
+    public void testEscapeAndUnescape(){
+        String s1="北京大学深圳研究生院";
+        String s2=StringHelper.escape(s1);
+        System.out.println(s2);
+        String s3=StringHelper.unescape(s2);
+        System.out.println(s3);
+        assertEquals(s1,s3);
+    }
+
+    @Test
+    public void testEscape(){
+        String s="-_~.a北京大学z深圳A研究生院Z";
+        String encoded=StringHelper.escape(s);
+        String want="-_~.a%E5%8C%97%E4%BA%AC%E5%A4%A7%E5%AD%A6z%E6%B7%B1%E5%9C%B3A%E7%A0%94%E7%A9%B6%E7%94%9F%E9%99%A2Z";
+        String decoded=StringHelper.unescape(encoded);
+        assertEquals(encoded,want);
+        assertEquals(decoded,s);
+    }
+
+    @Test
+    public void testEscape2(){
+        String s="-_~.azAZ09";
+        String encoded=StringHelper.escape(s);
+        String want="-_~.azAZ09";
+        String decoded=StringHelper.unescape(encoded);
+        assertEquals(encoded,want);
+        assertEquals(decoded,s);
+    }
+}