Convert between byte arrays and hexadecimal strings

 package com.example.demo.im;

    
  
    
 public class ByteUtils {
    
     private static final char[] HEX_CHAR = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
    
  
    
     /** * 方法四：byte[]-->hexString
    
      * * @param bytes
    
      * @return
    
      */
    
  
    
     public static String toHexString(byte[] bytes) {
    
     StringBuilder sb = new StringBuilder(bytes.length * 2);
    
 // 使用String的format方法进行转换
    
     for (byte b : bytes) {
    
         Integer value = b & 0xff;
    
         sb.append(String.format("%02x", va