Base64问题

[qq_23660243]

最近遇到加密问题 用到base64 看到前辈写的一个加密方法 但是真心看的不是很懂 求大神讲讲 讲的好孤身上这点分就全送

	static public String encode(byte[] data) {
			char[] out = new char[((data.length + 2) / 3) * 4];
			for (int i = 0, index = 0; i < data.length; i += 3, index += 4) {
				boolean quad = false;
				boolean trip = false;
				int val = (0xFF & (int) data[i]);
				val <<= 8;
				if ((i + 1) < data.length) {
					val |= (0xFF & (int) data[i + 1]);
					trip = true;
				}
				val <<= 8;
				if ((i + 2) < data.length) {
					val |= (0xFF & (int) data[i + 2]);
					quad = true;
				}
				out[index + 3] = alphabet[(quad ? (val & 0x3F) : 64)];
				val >>= 6;
				out[index + 2] = alphabet[(trip ? (val & 0x3F) : 64)];
				val >>= 6;
				out[index + 1] = alphabet[val & 0x3F];
				val >>= 6;
				out[index + 0] = alphabet[val & 0x3F];
			}
			
			return new String(out);
		}