二进制数与十六进制数之间如何互相转换

package com.demo;

/**
 * 进制转换
 * @Author: zhouhe
 * @Date: 2019/7/18 12:00
 */
public class HexUtil {
    /**
     * 二进制byte数组转十六进制byte数组
     * byte array to hex
     *
     * @param b byte array
     * @return hex string
     */
    public static String byte2hex(byte[] b) {
        StringBuilder hs = new StringBuilder();
        String stmp;
        for (int i = 0; i < b.length; i++) {
            stmp = Integer.toHexString(b[i] & 0xFF).toUpperCase();
            if (stmp.length() == 1) {
                hs.append("0").append(stmp);
            } else {
                hs.append(stmp);
            }
        }
        return hs.toString();
    }

    /**
     * 十六进制byte数组转二进制byte数组
     * hex to byte array
     *
     * @param hex hex string
     * @return byte array
     */
    public static byte[] hex2byte(String hex)
            throws IllegalArgumentException{
        if (hex.length() % 2 != 0) {
            throw new IllegalArgumentException ("invalid hex string");
        }
        char[] arr = hex.toCharArray();
        byte[] b = new byte[hex.length() / 2];
        for (int i = 0, j = 0, l = hex.length(); i < l; i++, j++) {
            String swap = "" + arr[i++] + arr[i];
            int byteint = Integer.parseInt(swap, 16) & 0xFF;
            b[j] = new Integer(byteint).byteValue();
        }
        return b;
    }

    public static void main(String[] args) {
        String str1 = "abcedefghijklmnopqrstuvwxyz";
        //String str1 = "1";
        String hexStr = HexUtil.byte2hex(str1.getBytes());
        System.out.println(hexStr);
        String str2 = new String(HexUtil.hex2byte(hexStr));
        System.out.println(str2);
        System.out.println(str1.equals(str2));
    }
}