Base64 kodieren und enkodieren mit Java4

public class Base64Coding
{
  private final static char[] ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".toCharArray();
  private static int[] toInt = new int[128];
 
  static
  {
    for (int i = 0; i < ALPHABET.length; i++)
    {
      toInt[ALPHABET[i]] = i;
    }
  }
 
  /**
   * Encodes the specified String into a Base64-String.
   *
   * @param String The string which should be encoded.
   * @return The Base64-encoded String
   */
  public static String encode(String string)
  {
    byte[] buf = string.getBytes();
    int size = buf.length;
    char[] ar = new char[((size + 2) / 3) * 4];
    int a = 0;
    int i = 0;
    while (i < size)
    {
      byte b0 = buf[i++];
      byte b1 = (i < size) ? buf[i++] : 0;
      byte b2 = (i < size) ? buf[i++] : 0;
 
      int mask = 0x3F;
      ar[a++] = ALPHABET[(b0 >> 2) & mask];
      ar[a++] = ALPHABET[((b0 << 4) | ((b1 & 0xFF) >> 4)) & mask];
      ar[a++] = ALPHABET[((b1 << 2) | ((b2 & 0xFF) >> 6)) & mask];
      ar[a++] = ALPHABET[b2 & mask];
    }
    switch (size % 3)
    {
      case 1:
        ar[--a] = '=';
      case 2:
        ar[--a] = '=';
    }
    return new String(ar);
  }
 
  /**
   * Decodes a Bas64-encoded String into a usual String.
   *
   * @param base64 The Base64-encoded String.
   * @return The Base64-decoded String.
   */
  public static String decode(String base64)
  {
    int delta = base64.endsWith("==") ? 2 : base64.endsWith("=") ? 1 : 0;
    byte[] buffer = new byte[base64.length() * 3 / 4 - delta];
    int mask = 0xFF;
    int index = 0;
    for (int i = 0; i < base64.length(); i += 4)
    {
      int c0 = toInt[base64.charAt(i)];
      int c1 = toInt[base64.charAt(i + 1)];
      buffer[index++] = (byte) (((c0 << 2) | (c1 >> 4)) & mask);
      if (index >= buffer.length)
      {
        return new String(buffer);
      }
      int c2 = toInt[base64.charAt(i + 2)];
      buffer[index++] = (byte) (((c1 << 4) | (c2 >> 2)) & mask);
      if (index >= buffer.length)
      {
        return new String(buffer);
      }
      int c3 = toInt[base64.charAt(i + 3)];
      buffer[index++] = (byte) (((c2 << 6) | c3) & mask);
    }
    return new String(buffer);
  }
}