base64的java實現方法

base64的編碼,解碼算法如下:

public class Base64 { /** * 將原始數據編碼爲base64編碼 */ static public char[] 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 out; } /** * 將base64編碼的數據解碼成原始數據 */ static public byte[] decode(char[] data) { int len = ((data.length + 3) / 4) * 3; if(data.length > 0 && data[data.length - 1] == '=') --len; if(data.length > 1 && data[data.length - 2] == '=') --len; byte[] out = new byte[len]; int shift = 0; int accum = 0; int index = 0; for(int ix = 0; ix < data.length; ix++) { int value = codes[data[ix] & 0xFF]; if(value >= 0) { accum <<= 6; shift += 6; accum |= value; if(shift >= 8) { shift -= 8; out[index++] = (byte)((accum >> shift) & 0xff); } } } if(index != out.length) throw new Error("miscalculated data length!"); return out; } static private char[] alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=".toCharArray(); static private byte[] codes = new byte[256]; static { for (int i = 0; i < 256; i++) codes[i] = -1; for (int i = 'A'; i <= 'Z'; i++) codes[i] = (byte) (i - 'A'); for (int i = 'a'; i <= 'z'; i++) codes[i] = (byte) (26 + i - 'a'); for (int i = '0'; i <= '9'; i++) codes[i] = (byte) (52 + i - '0'); codes['+'] = 62; codes['/'] = 63; } public static void main(String[] args) throws Exception { //加密成base64 String strSrc = "林"; String strOut = new String(Base64.encode(strSrc.getBytes())); System.out.println(strOut); String strOut2 = new String(Base64.decode(strOut.toCharArray())); System.out.println(strOut2); } }