Java将字节转换为十六进制代码分享

本文部分代码摘录自网上，并稍加整理，用于字节与十六进制之间的转换。

public class Hex {
 
  
  private static final char[] DIGITS_LOWER = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
      'a', 'b', 'c', 'd', 'e', 'f' };
 
  
  private static final char[] DIGITS_UPPER = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
      'A', 'B', 'C', 'D', 'E', 'F' };
 
  
  public static char[] encodeHex(final byte[] data) {
    return encodeHex(data, true);
  }
 
  
  public static char[] encodeHex(final byte[] data, final boolean toLowerCase) {
    return encodeHex(data, toLowerCase ? DIGITS_LOWER : DIGITS_UPPER);
  }
 
  
  protected static char[] encodeHex(final byte[] data, final char[] toDigits) {
    int l = data.length;
    char[] out = new char[l << 1];
    // two characters form the hex value.
    for (int i = 0, j = 0; i < l; i++) {
      out[j++] = toDigits[(0xF0 & data[i]) >>> 4];
      out[j++] = toDigits[0x0F & data[i]];
    }
    return out;
  }
 
  
  public static String encodeHexStr(final byte[] data) {
    return encodeHexStr(data, true);
  }
 
  
  public static String encodeHexStr(byte[] data, boolean toLowerCase) {
    return encodeHexStr(data, toLowerCase ? DIGITS_LOWER : DIGITS_UPPER);
  }
 
  
  protected static String encodeHexStr(byte[] data, char[] toDigits) {
    return new String(encodeHex(data, toDigits));
  }
 
  
  public static byte[] decodeHex(char[] data) {
    int len = data.length;
 
    if ((len & 0x01) != 0) {
      throw new RuntimeException("Odd number of characters.");
    }
 
    // 一个byte对应两个十六进制字符，则将byte[]大小设置为char[]大小的一半
    byte[] out = new byte[len >> 1];
 
    // two characters form the hex value.
    for (int i = 0, j = 0; j < len; i++) {
      int f = toDigit(data[j], j) << 4;
      j++;
      f = f | toDigit(data[j], j);
      j++;
      out[i] = (byte) (f & 0xFF);
    }
 
    return out;
  }
 
  
  protected static int toDigit(final char ch, final int index) {
    final int digit = Character.digit(ch, 16);
    if (digit == -1) {
      throw new RuntimeException("Illegal hexadecimal character " + ch + " at index " + index);
    }
    return digit;
  }
 
  public static void main(String[] args) {
    String srcStr = "HelloWorld!";
    String encodeStr = encodeHexStr(srcStr.getBytes(), false);
    String decodeStr = new String(decodeHex(encodeStr.toCharArray()));
    System.out.println("源字符串：" + srcStr);
    System.out.println("字符串编码为十六进制：" + encodeStr);
    System.out.println("十六进制解码为字符串：" + decodeStr);
  }
 
}