diff --git a/src/MD5.java b/src/MD5.java
new file mode 100644
index 0000000000000000000000000000000000000000..42f026c3bb97df4539c725e62ffcd3af7949eafe
--- /dev/null
+++ b/src/MD5.java
@@ -0,0 +1,42 @@
+import java.security.MessageDigest;
+import java.util.logging.Logger;
+
+/**
+ * MD5加密算法
+ */
+public class MD5 {
+
+    public static String MD5(String key) {
+        char hexDigits[] = {
+                '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'
+        };
+        try {
+            byte[] btInput = key.getBytes();
+            // 获得MD5摘要算法的 MessageDigest 对象
+            MessageDigest mdInst = MessageDigest.getInstance("MD5");
+            // 使用指定的字节更新摘要
+            mdInst.update(btInput);
+            // 获得密文
+            byte[] md = mdInst.digest();
+            // 把密文转换成十六进制的字符串形式
+            int j = md.length;
+            char str[] = new char[j * 2];
+            int k = 0;
+            for (int i = 0; i < j; i++) {
+                byte byte0 = md[i];
+                str[k++] = hexDigits[byte0 >>> 4 & 0xf];
+                str[k++] = hexDigits[byte0 & 0xf];
+            }
+            return new String(str);
+        } catch (Exception e) {
+            return null;
+        }
+    }
+
+    public static void main(String[] args){
+
+        String MD5_String;
+        MD5_String = MD5("weiqingde");
+        System.out.println(MD5_String);
+    }
+}
\ No newline at end of file
diff --git a/src/encryption/EncrypDDD.java b/src/encryption/EncrypDDD.java
new file mode 100644
index 0000000000000000000000000000000000000000..fded77328851ee016f65c69cdc89e687edf81e51
--- /dev/null
+++ b/src/encryption/EncrypDDD.java
@@ -0,0 +1,88 @@
+package encryption;
+
+import java.security.InvalidKeyException;
+import java.security.NoSuchAlgorithmException;
+import java.security.Security;
+
+import javax.crypto.BadPaddingException;
+import javax.crypto.Cipher;
+import javax.crypto.IllegalBlockSizeException;
+import javax.crypto.KeyGenerator;
+import javax.crypto.NoSuchPaddingException;
+import javax.crypto.SecretKey;
+
+public class EncrypDDD {
+
+	//KeyGenerator 提供对称密钥生成器的功能，支持各种算法
+		private KeyGenerator keygen;
+		//SecretKey 负责保存对称密钥
+		private SecretKey deskey;
+		//Cipher负责完成加密或解密工作
+		private Cipher c;
+		//该字节数组负责保存加密的结果
+		private byte[] cipherByte;
+		
+		public EncrypDDD() throws NoSuchAlgorithmException, NoSuchPaddingException{
+			Security.addProvider(new com.sun.crypto.provider.SunJCE());
+			//实例化支持DES算法的密钥生成器(算法名称命名需按规定，否则抛出异常)
+			keygen = KeyGenerator.getInstance("DES");
+			//生成密钥
+			deskey = keygen.generateKey();
+			//生成Cipher对象,指定其支持的DES算法
+			c = Cipher.getInstance("DES");
+		}
+		
+		/**
+		 * 对字符串加密
+		 * @param str
+		 * @return
+		 * @throws InvalidKeyException
+		 * @throws IllegalBlockSizeException
+		 * @throws BadPaddingException
+		 */
+		public byte[] Encrytor(String str) throws InvalidKeyException,
+				IllegalBlockSizeException, BadPaddingException {
+			// 根据密钥，对Cipher对象进行初始化，ENCRYPT_MODE表示加密模式
+			c.init(Cipher.ENCRYPT_MODE, deskey);
+			byte[] src = str.getBytes();
+			// 加密，结果保存进cipherByte
+			cipherByte = c.doFinal(src);
+			return cipherByte;
+		}
+
+		/**
+		 * 对字符串解密
+		 * 
+		 * @param buff
+		 * @return
+		 * @throws InvalidKeyException
+		 * @throws IllegalBlockSizeException
+		 * @throws BadPaddingException
+		 */
+		public byte[] Decryptor(byte[] buff) throws InvalidKeyException,
+				IllegalBlockSizeException, BadPaddingException {
+			// 根据密钥，对Cipher对象进行初始化，DECRYPT_MODE表示加密模式
+			c.init(Cipher.DECRYPT_MODE, deskey);
+			cipherByte = c.doFinal(buff);
+			return cipherByte;
+		}
+
+		/**
+		 * @param args
+		 * @throws NoSuchPaddingException 
+		 * @throws NoSuchAlgorithmException 
+		 * @throws BadPaddingException 
+		 * @throws IllegalBlockSizeException 
+		 * @throws InvalidKeyException 
+		 */
+		public static void main(String[] args) throws Exception {
+			EncrypDES de1 = new EncrypDES();
+			String msg ="郭XX-搞笑相声全集";
+			byte[] encontent = de1.Encrytor(msg);
+			byte[] decontent = de1.Decrytor(encontent);
+			System.out.println("明文是:" + msg);
+			System.out.println("加密后:" + new String(encontent));
+			System.out.println("解密后:" + new String(decontent));
+		}
+
+}
diff --git a/src/encryption/EncrypDES.java b/src/encryption/EncrypDES.java
new file mode 100644
index 0000000000000000000000000000000000000000..fadcc908e49b3956366865d937e5344fc7c1a5b3
--- /dev/null
+++ b/src/encryption/EncrypDES.java
@@ -0,0 +1,78 @@
+package encryption;
+
+import java.security.InvalidKeyException;
+import java.security.NoSuchAlgorithmException;
+import java.security.Security;
+
+import javax.crypto.BadPaddingException;
+import javax.crypto.Cipher;
+import javax.crypto.IllegalBlockSizeException;
+import javax.crypto.KeyGenerator;
+import javax.crypto.NoSuchPaddingException;
+import javax.crypto.SecretKey;
+/**
+ * DES加密算法
+ * DES是一种对称加密算法
+ * 采用单钥密码系统的加密方法，同一个密钥可以同时用作信息的加密和解密，
+ * 这种加密方法称为对称加密，也称为单密钥加密。 
+ * @author AI
+ * 2018年11月8日-下午3:05:20
+ */
+public class EncrypDES {
+	//KeyGenerator 提供对称密钥生成器的功能，支持各种算法
+	private KeyGenerator keygen;
+	//SecretKey 负责保存对称密钥
+	private SecretKey deskey;
+	//Cipher负责完成加密或解密工作
+	private Cipher c;
+	//该字节数组负责保存加密的结果
+	private byte[] cipherByte;
+	
+	/**
+	 * 被创建时初始化参数
+	 */
+	public EncrypDES() throws NoSuchAlgorithmException, NoSuchPaddingException {
+		Security.addProvider(new com.sun.crypto.provider.SunJCE());
+		//实例化支持DES算法的密钥生成器(算法名称命名需按规定，否则抛出异常)
+		keygen = KeyGenerator.getInstance("DES");
+		//生成密钥
+		deskey = keygen.generateKey();
+		//生成Cipher对象,指定其支持的DES算法
+		c = Cipher.getInstance("DES");
+	}
+	
+	/**
+	 * 对字符串加密
+	 * @param str    需要加密的字符串
+	 * @return
+	 * @throws InvalidKeyException
+	 * @throws IllegalBlockSizeException
+	 * @throws BadPaddingException
+	 */
+	public byte[] Encrytor(String str) throws InvalidKeyException,
+	IllegalBlockSizeException, BadPaddingException {
+		// 根据密钥，对Cipher对象进行初始化，ENCRYPT_MODE表示加密模式
+		c.init(Cipher.ENCRYPT_MODE, deskey);
+		byte[] src = str.getBytes();
+		System.out.println(new String(src));
+		// 加密，结果保存进cipherByte
+		cipherByte = c.doFinal(src);
+		return cipherByte;
+	}
+	
+	/**
+	 * 做解密
+	 * @param buff
+	 * @return
+	 * @throws InvalidKeyException
+	 * @throws IllegalBlockSizeException
+	 * @throws BadPaddingException
+	 */
+	public byte[] Decrytor(byte[] buff) throws InvalidKeyException,
+	IllegalBlockSizeException, BadPaddingException {
+		c.init(Cipher.ENCRYPT_MODE, deskey);
+		cipherByte = c.doFinal(buff);
+		return cipherByte;
+	}
+	
+}
diff --git a/src/encryption/MD5.java b/src/encryption/MD5.java
new file mode 100644
index 0000000000000000000000000000000000000000..0c62b802104c5cf751d7e1bc7d3e1169da5e4e23
--- /dev/null
+++ b/src/encryption/MD5.java
@@ -0,0 +1,30 @@
+package encryption;
+
+import java.io.UnsupportedEncodingException;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+
+import sun.misc.BASE64Encoder;
+
+public class MD5 {
+
+	 /**利用MD5进行加密*/
+    public String EncoderByMd5(String str) throws NoSuchAlgorithmException, UnsupportedEncodingException{
+        //确定计算方法
+        MessageDigest md5=MessageDigest.getInstance("MD5");
+        BASE64Encoder base64en = new BASE64Encoder();
+        //加密后的字符串
+        String newstr=base64en.encode(md5.digest(str.getBytes("utf-8")));
+        return newstr;
+    }
+    
+    /**判断用户密码是否正确
+     *newpasswd  用户输入的密码
+     *oldpasswd  正确密码*/
+    public boolean checkpassword(String newpasswd,String oldpasswd) throws NoSuchAlgorithmException, UnsupportedEncodingException{
+        if(EncoderByMd5(newpasswd).equals(oldpasswd))
+            return true;
+        else
+            return false;
+    }
+}
diff --git a/src/encryption/TanXin.java b/src/encryption/TanXin.java
new file mode 100644
index 0000000000000000000000000000000000000000..232a4785a10c6bd25c346b5f734634ab96ea8427
--- /dev/null
+++ b/src/encryption/TanXin.java
@@ -0,0 +1,27 @@
+package encryption;
+
+public class TanXin {
+
+	public static void main(String[] args) {
+		String str = sub(2,"15735896");
+		System.out.println(str);
+	}
+	public static String sub(int x,String num) {
+		String tNum = num;
+		boolean has = false;
+		for(int j=0;j<x;j++) {
+			for(int i=0;i<num.length()-1;i++) {
+				if(tNum.charAt(i)>tNum.charAt(i+1)) {
+					tNum = tNum.substring(0, i)+tNum.substring(i+1);
+					has = true;
+					break;
+				}
+			}
+			if(!has) {
+				tNum = tNum.substring(0, tNum.length());
+			}
+		}
+		return tNum;
+	}
+	
+}
diff --git a/src/encryption/TestEncryption.java b/src/encryption/TestEncryption.java
new file mode 100644
index 0000000000000000000000000000000000000000..d30b071894130c60b531fd6e1aa0adde30674a38
--- /dev/null
+++ b/src/encryption/TestEncryption.java
@@ -0,0 +1,127 @@
+package encryption;
+
+import java.security.InvalidKeyException;
+import java.security.NoSuchAlgorithmException;
+
+import javax.crypto.BadPaddingException;
+import javax.crypto.IllegalBlockSizeException;
+import javax.crypto.NoSuchPaddingException;
+
+import org.junit.jupiter.api.Test;
+
+public class TestEncryption {
+
+	@Test
+	public void testDes() throws NoSuchAlgorithmException, NoSuchPaddingException {
+		EncrypDES e1 = new EncrypDES();
+		try {
+			String str = "ccc";
+			byte[] b1 = e1.Encrytor("abc");
+			System.out.println("#####加密之后：" + new String(b1));
+			byte[] b2 = e1.Decrytor(b1);
+			System.out.println("#####解密：" + new String(b2));
+		} catch (InvalidKeyException e) {
+			e.printStackTrace();
+		} catch (IllegalBlockSizeException e) {
+			e.printStackTrace();
+		} catch (BadPaddingException e) {
+			e.printStackTrace();
+		}
+	}
+
+	@Test
+	public void tess() throws InvalidKeyException, IllegalBlockSizeException, BadPaddingException {
+		EncrypDES de1;
+		try {
+			de1 = new EncrypDES();
+			String msg = "郭XX-搞笑相声全集";
+			byte[] encontent = de1.Encrytor(msg);
+			byte[] decontent = de1.Decrytor(encontent);
+			System.out.println("明文是:" + msg);
+			System.out.println("加密后:" + new String(encontent));
+			System.out.println("解密后:" + new String(decontent));
+		} catch (NoSuchAlgorithmException | NoSuchPaddingException e) {
+			e.printStackTrace();
+		}
+
+	}
+
+	@Test
+	public void test2() throws NoSuchAlgorithmException, NoSuchPaddingException {
+		EncrypDES e1 = new EncrypDES();
+		try {
+			byte[] b1 = e1.Encrytor("abc");
+			System.out.println("#####加密之后：" + new String(b1));
+			byte[] b2 = e1.Decrytor(b1);
+			System.out.println("#####解密：" + new String(b2));
+		} catch (InvalidKeyException e) {
+			e.printStackTrace();
+		} catch (IllegalBlockSizeException e) {
+			e.printStackTrace();
+		} catch (BadPaddingException e) {
+			e.printStackTrace();
+		}
+	}
+
+	@Test
+	public void testMD5() {
+		MD5 md = new MD5();
+		String str = "apple";
+		try {
+			String newString = md.EncoderByMd5(str);
+			System.out.println(newString);
+		} catch (Exception e) {
+
+		}
+	}
+
+	@Test
+	public void asd() {
+		String str = removeKDigits1("1432219", 3);
+		System.out.println(str);
+	}
+
+	public static String removeKdigits(String num, int k) {
+		int len = num.length() - k;
+		char[] stack = new char[len];
+		for (int i = 0; i < num.length(); i++) {
+			char c = num.charAt(i);
+			while (k > 0 && stack[k - 1] > c) {
+				k--;
+			}
+			stack[k + 1] = c;
+		}
+		int x = 0;
+		while (x < len && stack[x] == '0') {
+			x++;
+		}
+		return x == len ? "0" : new String(stack, x, len - x);
+	}
+
+	public static String removeKDigits1(String num,int k){
+
+		// 新整数的最终长度 = 原整数长度 - k
+		int newLength = num.length()- k;
+		// 创建一个栈，用于接收所有的数字
+		char[] stack =new char[num.length()];
+		int top =0;
+		for(int i =0; i < num.length();++i){
+			// 遍历当前数字
+			char c = num.charAt(i);
+			// 当栈顶数字大于遍历到的当前数字，栈顶数字出栈（相当于删除数字）
+			while(top >0&& stack[top - 1]> c && k >0){
+				top -=1;
+				k -=1;
+			}
+			// 遍历到的当前数字入栈
+			stack[top++]= c;
+		}
+		// 找到栈中第一个非零数字的位置，以此构建新的整数字符串
+		int offset =0;
+		while(offset < newLength && stack[offset]=='0'){
+			offset++;
+		}
+		return offset == newLength ?"0" :new String(stack, offset, newLength - offset);
+	}
+
+}
diff --git a/src/testMD5.java b/src/testMD5.java
new file mode 100644
index 0000000000000000000000000000000000000000..25cc028aaa5807d11aaced67d66007c0ee77103f
--- /dev/null
+++ b/src/testMD5.java
@@ -0,0 +1,52 @@
+import java.security.MessageDigest;
+import java.sql.Time;
+
+import org.junit.jupiter.api.Test;
+
+public class testMD5 {
+	private static String[] hexDigits = { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e","f" };
+
+	public static void main(String[] args) throws Exception {
+		String str = "abc123";
+		String str1 = MD5Encode(str);
+		System.out.println(str1);
+	}
+
+	public static String byteArrayTOHexDigitsString(byte[] b) {
+    	StringBuffer sb = new StringBuffer();
+    	for(int i = 0;i < b.length; i++) {
+    		sb.append(buteTOHexDigitsString(b[i]));
+    	}
+    	return null;
+    }
+	
+	public static String buteTOHexDigitsString(byte ss) {
+		int n = ss;
+		if(n < 0) {
+			n+=256;
+		}
+		int d1 = n/16;
+		int d2 = n%16;
+		return hexDigits[d1]+hexDigits[d2];
+	}
+	
+	public static String MD5Encode(String pwd) throws Exception{
+		String result = null;
+		try {
+			result = new String(pwd);
+			MessageDigest md = MessageDigest.getInstance("MD5");
+			System.out.println("****************"+result);
+			result = byteArrayTOHexDigitsString(md.digest(result.getBytes()));
+			System.out.println("$$$$$$$$$$$$$44444"+result);
+		}catch(Exception e) {
+			e.printStackTrace();
+		}
+		System.out.println("#############"+result);
+		return result;
+	}
+	
+	@Test
+	public void timmme() {
+		System.out.println(new Time(System.currentTimeMillis()));
+	}
+}