java byte数组与16进制间相互转换的示例

import java.util.Arrays;

/**
 * Byte[]与hex的相互转换
 * @explain
 * @author Marydon
 * @creationTime 2018年6月11日下午2:29:11
 * @version 1.0
 * @since
 * @email marydon20170307@163.com
 */
public class ByteUtils {

  // 16进制字符
  private static final char[] HEX_CHAR = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
}

/**
 * 方法一：将byte类型数组转化成16进制字符串
 * @explain 字符串拼接
 * @param bytes
 * @return
 */
public static String toHexString(byte[] bytes) {
  StringBuilder sb = new StringBuilder();
  int num;
  for (byte b : bytes) {
    num = b < 0 ? 256 + b : b;
    sb.append(HEX_CHAR[num / 16]).append(HEX_CHAR[num % 16]);
  }
  return sb.toString();
}

/**
 * 方法二： byte[] to hex string
 * @explain 使用数组
 * @param bytes
 * @return
 */
public static String toHexString2(byte[] bytes) {
  // 一个byte为8位，可用两个十六进制位表示
  char[] buf = new char[bytes.length * 2];
  int a = 0;
  int index = 0;
  // 使用除与取余进行转换
  for (byte b : bytes) {
    if (b < 0)
      a = 256 + b;
    else
      a = b;

    // 偶数位用商表示
    buf[index++] = HEX_CHAR[a / 16];
    // 奇数位用余数表示
    buf[index++] = HEX_CHAR[a % 16];
  }
  // char[]-->String
  return new String(buf);
}

/**
 * 方法三： byte[]-->hexString
 * @explain 使用位运算
 * @param bytes
 * @return
 */
public static String toHexString3(byte[] bytes) {
  char[] buf = new char[bytes.length * 2];
  int index = 0;
  // 利用位运算进行转换，可以看作方法二的变型
  for (byte b : bytes) {
    buf[index++] = HEX_CHAR[b >>> 4 & 0xf];
    buf[index++] = HEX_CHAR[b & 0xf];
  }

  return new String(buf);
}

/**
 * 方法四：byte[]-->hexString
 * @param bytes
 * @return
 */
public static String toHexString4(byte[] bytes) {
  StringBuilder sb = new StringBuilder(bytes.length * 2);
  // 使用String的format方法进行转换
  for (byte b : bytes) {
    sb.append(String.format("%02x", new Integer(b & 0xff)));
  }

  return sb.toString();
}

/**
 * 将byte数组转换成16进制字符串
 *
 * @param src
 * @return
 */
private static String bytesToHexString(byte[] src) {
  StringBuilder sb = new StringBuilder();
  for (int i = 0; i < src.length; i++) {
    int v = src[i] & 0xFF;
    String hv = Integer.toHexString(v);
    if (hv.length() < 2) {
      sb.append(0);
    }
    sb.append(hv);
  }
  return sb.toString();
}　　

/**
 * 将16进制字符串转换为byte[]
 * @explain 16进制字符串不区分大小写，返回的数组相同
 * @param hexString
 *      16进制字符串
 * @return byte[]
 */
public static byte[] fromHexString(String hexString) {
  if (null == hexString || "".equals(hexString.trim())) {
    return new byte[0];
  }

  byte[] bytes = new byte[hexString.length() / 2];
  // 16进制字符串
  String hex;
  for (int i = 0; i < hexString.length() / 2; i++) {
    // 每次截取2位
    hex = hexString.substring(i * 2, i * 2 + 2);
    // 16进制-->十进制
    bytes[i] = (byte) Integer.parseInt(hex, 16);
  }

  return bytes;
}

/**
 * 将16进制转换为byte[]
 * @param hexStr
 * @return
 */
public static byte[] fromHex(String hexStr) {
  if (hexStr.length() < 1)
    return null;
  byte[] result = new byte[hexStr.length() / 2];
  for (int i = 0; i < hexStr.length() / 2; i++) {
    int high = Integer.parseInt(hexStr.substring(i * 2, i * 2 + 1), 16);
    int low = Integer.parseInt(hexStr.substring(i * 2 + 1, i * 2 + 2), 16);
    result[i] = (byte) (high * 16 + low);
  }
  return result;
}

public static byte[] toByteArray(String data) {
    if (data == null) {
        return new byte[] {};
    }
    if (data.length() == 0) {
        return new byte[] {};
    }
    while (data.length() < 2) {
        data = "0" + data;
    }
    if (data.substring(0, 2).toLowerCase().equals("0x")) {
        data = data.substring(2);
    }
    if (data.length() % 2 == 1) {
        data = "0" + data;
    }
    data = data.toUpperCase();
    byte[] bytes = new byte[data.length() / 2];
    String hexString = "0123456789ABCDEF";
    for (int i = 0; i < bytes.length; i++) {
        int byteConv = hexString.indexOf(data.charAt(i * 2)) * 0x10;
        byteConv += hexString.indexOf(data.charAt(i * 2 + 1));
        bytes[i] = (byte) (byteConv & 0xFF);
    }
    return bytes;
}　　

public static void main(String[] args) throws Exception {
  String json = "{\"name\":\"Marydon\",\"website\":\"http://www.cnblogs.com/Marydon20170307\"}";
  byte[] bytes = json.getBytes("utf-8");
  System.out.println("字节数组为：" + Arrays.toString(bytes));
  System.out.println("byte数组转16进制之方法一：" + toHexString(bytes));
  System.out.println("byte数组转16进制之方法二：" + ByteUtils.toHexString2(bytes));
  System.out.println("byte数组转16进制之方法三：" + ByteUtils.toHexString3(bytes));
  System.out.println("byte数组转16进制之方法四：" + ByteUtils.toHexString4(bytes));
  System.out.println("==================================");
  String str = "7b226e616d65223a224d617279646f6e222c2277656273697465223a22687474703a2f2f7777772e636e626c6f67732e636f6d2f4d617279646f6e3230313730333037227d";
  System.out.println("转换后的字节数组：" + Arrays.toString(fromHexString(str)));
  System.out.println(new String(fromHexString(str), "utf-8"));
}