Base64编码认识（Java 测试）
简述：
Base64的一个转码的实现
原理：
Base64编码方法要求把每三个8Bit的字节转换为四个6Bit的字节，其中，转换之后的这四个字节中每6个有效bit为是有效数据，空余的那两个 bit用0补上成为一个字节
例如，有三个字节的原始数据：aaaaaabb bbbbccccc ccdddddd（这里每个字母表示一个bit位）
那么编码之后会变成： 00aaaaaa 00bbbbbb 00cccccc 00dddddd
如果再看一下实际的0、1bit位操作，
转换前 10101101 10111010 01110110
转换后 00101011 00011011 00101001 00110110
所以冗余量不大，只会多出来三分之一长
此外如果原文的byte数不是3的整倍数，则用（3 -（byteLength % 3）） 数量的等号不足
代码：
Base64.java
package testBase64;
import java.util.Arrays;
/** A very fast and memory efficient class to encode and decode to and from BASE64 in full accordance
* with RFC 2045.<br><br>
* On Windows XP sp1 with 1.4.2_04 and later ;), this encoder and decoder is about 10 times faster
* on small arrays (10 - 1000 bytes) and 2-3 times as fast on larger arrays (10000 - 1000000 bytes)
* compared to <code>sun.misc.Encoder()/Decoder()</code>.<br><br>
*
* On byte arrays the encoder is about 20% faster than Jakarta Commons Base64 Codec for encode and
* about 50% faster for decoding large arrays. This implementation is about twice as fast on very small
* arrays (< 30 bytes). If source/destination is a <code>String</code> this
* version is about three times as fast due to the fact that the Commons Codec result has to be recoded
* to a <code>String</code> from <code>byte[]</code>, which is very expensive.<br><br>
*
* This encode/decode algorithm doesn't create any temporary arrays as many other codecs do, it only
* allocates the resulting array. This produces less garbage and it is possible to handle arrays twice
* as large as algorithms that create a temporary array. (E.g. Jakarta Commons Codec). It is unknown
* whether Sun's <code>sun.misc.Encoder()/Decoder()</code> produce temporary arrays but since performance
* is quite low it probably does.<br><br>
*
* The encoder produces the same output as the Sun one except that the Sun's encoder appends
* a trailing line separator if the last character isn't a pad. Unclear why but it only adds to the
* length and is probably a side effect. Both are in conformance with RFC 2045 though.<br>
* Commons codec seem to always att a trailing line separator.<br><br>
*
* <b>Note!</b>
* The encode/decode method pairs (types) come in three versions with the <b>exact</b> same algorithm and
* thus a lot of code redundancy. This is to not create any temporary arrays for transcoding to/from different
* format types. The methods not used can simply be commented out.<br><br>
*
* There is also a "fast" version of all decode methods that works the same way as the normal ones, but
* har a few demands on the decoded input. Normally though, these fast verions should be used if the source if
* the input is known and it hasn't bee tampered with.<br><br>
*
* If you find the code useful or you find a bug, please send me a note at base64 @ miginfocom . com.
*
* Licence (BSD):
* ==============
*
* Copyright (c) 2004, Mikael Grev, MiG InfoCom AB. (base64 @ miginfocom . com)
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modification,
* are permitted provided that the following conditions are met:
* Redistributions of source code must retain the above copyright notice, this list
* of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright notice, this
* list of conditions and the following disclaimer in the documentation and/or other
* materials provided with the distribution.
* Neither the name of the MiG InfoCom AB nor the names of its contributors may be
* used to endorse or promote products derived from this software without specific
* prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
* OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
* OF SUCH DAMAGE.
*
* @version 2.2
* @author Mikael Grev
* Date: 2004-aug-02
* Time: 11:31:11
*/
public class Base64
{
private static final char[] CA = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".toCharArray();
private static final int[] IA = new int[256];
static {
Arrays.fill(IA, -1);
for (int i = 0, iS = CA.length; i < iS; i++)
IA[CA[i]] = i;
IA['='] = 0;
}
// ****************************************************************************************
// * char[] version
// ****************************************************************************************
/** Encodes a raw byte array into a BASE64 <code>char[]</code> representation i accordance with RFC 2045.
* @param sArr The bytes to convert. If <code>null</code> or length 0 an empty array will be returned.
* @param lineSep Optional "\r\n" after 76 characters, unless end of file.<br>
* No line separator will be in breach of RFC 2045 which specifies max 76 per line but will be a
* little faster.
* @return A BASE64 encoded array. Never <code>null</code>.
*/
public final static char[] encodeToChar(byte[] sArr, boolean lineSep)
{
// Check special case
int sLen = sArr != null ? sArr.length : 0;
if (sLen == 0)
return new char[0];
int eLen = (sLen / 3) * 3; // Length of even 24-bits.
int cCnt = ((sLen - 1) / 3 + 1) << 2; // Returned character count
int dLen = cCnt + (lineSep ? (cCnt - 1) / 76 << 1 : 0); // Length of returned array
char[] dArr = new char[dLen];
// Encode even 24-bits
for (int s = 0, d = 0, cc = 0; s < eLen;) {
// Copy next three bytes into lower 24 bits of int, paying attension to sign.
int i = (sArr[s++] & 0xff) << 16 | (sArr[s++] & 0xff) << 8 | (sArr[s++] & 0xff);
// Encode the int into four chars
dArr[d++] = CA[(i >>> 18) & 0x3f];
dArr[d++] = CA[(i >>> 12) & 0x3f];
dArr[d++] = CA[(i >>> 6) & 0x3f];
dArr[d++] = CA[i & 0x3f];
// Add optional line separator
if (lineSep && ++cc == 19 && d < dLen - 2) {
dArr[d++] = '\r';
dArr[d++] = '\n';
cc = 0;
}
}
// Pad and encode last bits if source isn't even 24 bits.
int left = sLen - eLen; // 0 - 2.
if (left > 0) {
// Prepare the int
int i = ((sArr[eLen] & 0xff) << 10) | (left == 2 ? ((sArr[sLen - 1] & 0xff) << 2) : 0);
// Set last four chars
dArr[dLen - 4] = CA[i >> 12];
dArr[dLen - 3] = CA[(i >>> 6) & 0x3f];
dArr[dLen - 2] = left == 2 ? CA[i & 0x3f] : '=';
dArr[dLen - 1] = '=';
}
return dArr;
}
/** Decodes a BASE64 encoded char array. All illegal characters will be ignored and can handle both arrays with
* and without line separators.
* @param sArr The source array. <code>null</code> or length 0 will return an empty array.
* @return The decoded array of bytes. May be of length 0. Will be <code>null</code> if the legal characters
* (including '=') isn't divideable by 4. (I.e. definitely corrupted).
*/
public final static byte[] decode(char[] sArr)
{
// Check special case
int sLen = sArr != null ? sArr.length : 0;
if (sLen == 0)
return new byte[0];
// Count illegal characters (including '\r', '\n') to know what size the returned array will be,
// so we don't have to reallocate & copy it later.
int sepCnt = 0; // Number of separator characters. (Actually illegal characters, but that's a bonus...)
for (int i = 0; i < sLen; i++) // If input is "pure" (I.e. no line separators or illegal chars) base64 this loop can be commented out.
if (IA[sArr[i]] < 0)
sepCnt++;
// Check so that legal chars (including '=') are evenly divideable by 4 as specified in RFC 2045.
if ((sLen - sepCnt) % 4 != 0)
return null;
int pad = 0;
for (int i = sLen; i > 1 && IA[sArr[--i]] <= 0;)
if (sArr[i] == '=')
pad++;
int len = ((sLen - sepCnt) * 6 >> 3) - pad;
byte[] dArr = new byte[len]; // Preallocate byte[] of exact length
for (int s = 0, d = 0; d < len;) {
// Assemble three bytes into an int from four "valid" characters.
int i = 0;
for (int j = 0; j < 4; j++) { // j only increased if a valid char was found.
int c = IA[sArr[s++]];
if (c >= 0)
i |= c << (18 - j * 6);
else
j--;
}
// Add the bytes
dArr[d++] = (byte) (i >> 16);
if (d < len) {
dArr[d++]= (byte) (i >> 8);
if (d < len)
dArr[d++] = (byte) i;
}
}
return dArr;
}
/** Decodes a BASE64 encoded char array that is known to be resonably well formatted. The method is about twice as
* fast as {@link #decode(char[])}. The preconditions are:<br>
* + The array must have a line length of 76 chars OR no line separators at all (one line).<br>
* + Line separator must be "\r\n", as specified in RFC 2045
* + The array must not contain illegal characters within the encoded string<br>
* + The array CAN have illegal characters at the beginning and end, those will be dealt with appropriately.<br>
* @param sArr The source array. Length 0 will return an empty array. <code>null</code> will throw an exception.
* @return The decoded array of bytes. May be of length 0.
*/
public final static byte[] decodeFast(char[] sArr)
{
// Check special case
int sLen = sArr.length;
if (sLen == 0)
return new byte[0];
int sIx = 0, eIx = sLen - 1; // Start and end index after trimming.
// Trim illegal chars from start
while (sIx < eIx && IA[sArr[sIx]] < 0)
sIx++;
// Trim illegal chars from end
while (eIx > 0 && IA[sArr[eIx]] < 0)
eIx--;
// get the padding count (=) (0, 1 or 2)
int pad = sArr[eIx] == '=' ? (sArr[eIx - 1] == '=' ? 2 : 1) : 0; // Count '=' at end.
int cCnt = eIx - sIx + 1; // Content count including possible separators
int sepCnt = sLen > 76 ? (sArr[76] == '\r' ? cCnt / 78 : 0) << 1 : 0;
int len = ((cCnt - sepCnt) * 6 >> 3) - pad; // The number of decoded bytes
byte[] dArr = new byte[len]; // Preallocate byte[] of exact length
// Decode all but the last 0 - 2 bytes.
int d = 0;
for (int cc = 0, eLen = (len / 3) * 3; d < eLen;) {
// Assemble three bytes into an int from four "valid" characters.
int i = IA[sArr[sIx++]] << 18 | IA[sArr[sIx++]] << 12 | IA[sArr[sIx++]] << 6 | IA[sArr[sIx++]];
// Add the bytes
dArr[d++] = (byte) (i >> 16);
dArr[d++] = (byte) (i >> 8);
dArr[d++] = (byte) i;
// If line separator, jump over it.
if (sepCnt > 0 && ++cc == 19) {
sIx += 2;
cc = 0;
}
}
if (d < len) {
// Decode last 1-3 bytes (incl '=') into 1-3 bytes
int i = 0;
for (int j = 0; sIx <= eIx - pad; j++)
i |= IA[sArr[sIx++]] << (18 - j * 6);
for (int r = 16; d < len; r -= 8)
dArr[d++] = (byte) (i >> r);
}
return dArr;
}
// ****************************************************************************************
// * byte[] version
// ****************************************************************************************
/** Encodes a raw byte array into a BASE64 <code>byte[]</code> representation i accordance with RFC 2045.
* @param sArr The bytes to convert. If <code>null</code> or length 0 an empty array will be returned.
* @param lineSep Optional "\r\n" after 76 characters, unless end of file.<br>
* No line separator will be in breach of RFC 2045 which specifies max 76 per line but will be a
* little faster.
* @return A BASE64 encoded array. Never <code>null</code>.
*/
public final static byte[] encodeToByte(byte[] sArr, boolean lineSep)
{
// Check special case
int sLen = sArr != null ? sArr.length : 0;
if (sLen == 0)
return new byte[0];
int eLen = (sLen / 3) * 3; // Length of even 24-bits.
int cCnt = ((sLen - 1) / 3 + 1) << 2; // Returned character count
int dLen = cCnt + (lineSep ? (cCnt - 1) / 76 << 1 : 0); // Length of returned array
byte[] dArr = new byte[dLen];
// Encode even 24-bits
for (int s = 0, d = 0, cc = 0; s < eLen;) {
// Copy next three bytes into lower 24 bits of int, paying attension to sign.
int i = (sArr[s++] & 0xff) << 16 | (sArr[s++] & 0xff) << 8 | (sArr[s++] & 0xff);
// Encode the int into four chars
dArr[d++] = (byte) CA[(i >>> 18) & 0x3f];
dArr[d++] = (byte) CA[(i >>> 12) & 0x3f];
dArr[d++] = (byte) CA[(i >>> 6) & 0x3f];
dArr[d++] = (byte) CA[i & 0x3f];
// Add optional line separator
if (lineSep && ++cc == 19 && d < dLen - 2) {
dArr[d++] = '\r';
dArr[d++] = '\n';
cc = 0;
}
}
// Pad and encode last bits if source isn't an even 24 bits.
int left = sLen - eLen; // 0 - 2.
if (left > 0) {
// Prepare the int
int i = ((sArr[eLen] & 0xff) << 10) | (left == 2 ? ((sArr[sLen - 1] & 0xff) << 2) : 0);
// Set last four chars
dArr[dLen - 4] = (byte) CA[i >> 12];
dArr[dLen - 3] = (byte) CA[(i >>> 6) & 0x3f];
dArr[dLen - 2] = left == 2 ? (byte) CA[i & 0x3f] : (byte) '=';
dArr[dLen - 1] = '=';
}
return dArr;
}
/** Decodes a BASE64 encoded byte array. All illegal characters will be ignored and can handle both arrays with
* and without line separators.
* @param sArr The source array. Length 0 will return an empty array. <code>null</code> will throw an exception.
* @return The decoded array of bytes. May be of length 0. Will be <code>null</code> if the legal characters
* (including '=') isn't divideable by 4. (I.e. definitely corrupted).
*/
public final static byte[] decode(byte[] sArr)
{
// Check special case
int sLen = sArr.length;
// Count illegal characters (including '\r', '\n') to know what size the returned array will be,
// so we don't have to reallocate & copy it later.
int sepCnt = 0; // Number of separator characters. (Actually illegal characters, but that's a bonus...)
for (int i = 0; i < sLen; i++) // If input is "pure" (I.e. no line separators or illegal chars) base64 this loop can be commented out.
if (IA[sArr[i] & 0xff] < 0)
sepCnt++;
// Check so that legal chars (including '=') are evenly divideable by 4 as specified in RFC 2045.
if ((sLen - sepCnt) % 4 != 0)
return null;
int pad = 0;
for (int i = sLen; i > 1 && IA[sArr[--i] & 0xff] <= 0;)
if (sArr[i] == '=')
pad++;
int len = ((sLen - sepCnt) * 6 >> 3) - pad;
byte[] dArr = new byte[len]; // Preallocate byte[] of exact length
for (int s = 0, d = 0; d < len;) {
// Assemble three bytes into an int from four "valid" characters.
int i = 0;
for (int j = 0; j < 4; j++) { // j only increased if a valid char was found.
int c = IA[sArr[s++] & 0xff];
if (c >= 0)
i |= c << (18 - j * 6);
else
j--;
}
// Add the bytes
dArr[d++] = (byte) (i >> 16);
if (d < len) {
dArr[d++]= (byte) (i >> 8);
if (d < len)
dArr[d++] = (byte) i;
}
}
return dArr;
}
/** Decodes a BASE64 encoded byte array that is known to be resonably well formatted. The method is about twice as
* fast as {@link #decode(byte[])}. The preconditions are:<br>
* + The array must have a line length of 76 chars OR no line separators at all (one line).<br>
* + Line separator must be "\r\n", as specified in RFC 2045
* + The array must not contain illegal characters within the encoded string<br>
* + The array CAN have illegal characters at the beginning and end, those will be dealt with appropriately.<br>
* @param sArr The source array. Length 0 will return an empty array. <code>null</code> will throw an exception.
* @return The decoded array of bytes. May be of length 0.
*/
public final static byte[] decodeFast(byte[] sArr)
{
// Check special case
int sLen = sArr.length;
if (sLen == 0)
return new byte[0];
int sIx = 0, eIx = sLen - 1; // Start and end index after trimming.
// Trim illegal chars from start
while (sIx < eIx && IA[sArr[sIx] & 0xff] < 0)
sIx++;
// Trim illegal chars from end
while (eIx > 0 && IA[sArr[eIx] & 0xff] < 0)
eIx--;
// get the padding count (=) (0, 1 or 2)
int pad = sArr[eIx] == '=' ? (sArr[eIx - 1] == '=' ? 2 : 1) : 0; // Count '=' at end.
int cCnt = eIx - sIx + 1; // Content count including possible separators
int sepCnt = sLen > 76 ? (sArr[76] == '\r' ? cCnt / 78 : 0) << 1 : 0;
int len = ((cCnt - sepCnt) * 6 >> 3) - pad; // The number of decoded bytes
byte[] dArr = new byte[len]; // Preallocate byte[] of exact length
// Decode all but the last 0 - 2 bytes.
int d = 0;
for (int cc = 0, eLen = (len / 3) * 3; d < eLen;) {
// Assemble three bytes into an int from four "valid" characters.
int i = IA[sArr[sIx++]] << 18 | IA[sArr[sIx++]] << 12 | IA[sArr[sIx++]] << 6 | IA[sArr[sIx++]];
// Add the bytes
dArr[d++] = (byte) (i >> 16);
dArr[d++] = (byte) (i >> 8);
dArr[d++] = (byte) i;
// If line separator, jump over it.
if (sepCnt > 0 && ++cc == 19) {
sIx += 2;
cc = 0;
}
}
if (d < len) {
// Decode last 1-3 bytes (incl '=') into 1-3 bytes
int i = 0;
for (int j = 0; sIx <= eIx - pad; j++)
i |= IA[sArr[sIx++]] << (18 - j * 6);
for (int r = 16; d < len; r -= 8)
dArr[d++] = (byte) (i >> r);
}
return dArr;
}
// ****************************************************************************************
// * String version
// ****************************************************************************************
/** Encodes a raw byte array into a BASE64 <code>String</code> representation i accordance with RFC 2045.
* @param sArr The bytes to convert. If <code>null</code> or length 0 an empty array will be returned.
* @param lineSep Optional "\r\n" after 76 characters, unless end of file.<br>
* No line separator will be in breach of RFC 2045 which specifies max 76 per line but will be a
* little faster.
* @return A BASE64 encoded array. Never <code>null</code>.
*/
public final static String encodeToString(byte[] sArr, boolean lineSep)
{
// Reuse char[] since we can't create a String incrementally anyway and StringBuffer/Builder would be slower.
return new String(encodeToChar(sArr, lineSep));
}
/** Decodes a BASE64 encoded <code>String</code>. All illegal characters will be ignored and can handle both strings with
* and without line separators.<br>
* <b>Note!</b> It can be up to about 2x the speed to call <code>decode(str.toCharArray())</code> instead. That
* will create a temporary array though. This version will use <code>str.charAt(i)</code> to iterate the string.
* @param str The source string. <code>null</code> or length 0 will return an empty array.
* @return The decoded array of bytes. May be of length 0. Will be <code>null</code> if the legal characters
* (including '=') isn't divideable by 4. (I.e. definitely corrupted).
*/
public final static byte[] decode(String str)
{
// Check special case
int sLen = str != null ? str.length() : 0;
if (sLen == 0)
return new byte[0];
// Count illegal characters (including '\r', '\n') to know what size the returned array will be,
// so we don't have to reallocate & copy it later.
int sepCnt = 0; // Number of separator characters. (Actually illegal characters, but that's a bonus...)
for (int i = 0; i < sLen; i++) // If input is "pure" (I.e. no line separators or illegal chars) base64 this loop can be commented out.
if (IA[str.charAt(i)] < 0)
sepCnt++;
// Check so that legal chars (including '=') are evenly divideable by 4 as specified in RFC 2045.
if ((sLen - sepCnt) % 4 != 0)
return null;
// Count '=' at end
int pad = 0;
for (int i = sLen; i > 1 && IA[str.charAt(--i)] <= 0;)
if (str.charAt(i) == '=')
pad++;
int len = ((sLen - sepCnt) * 6 >> 3) - pad;
byte[] dArr = new byte[len]; // Preallocate byte[] of exact length
for (int s = 0, d = 0; d < len;) {
// Assemble three bytes into an int from four "valid" characters.
int i = 0;
for (int j = 0; j < 4; j++) { // j only increased if a valid char was found.
int c = IA[str.charAt(s++)];
if (c >= 0)
i |= c << (18 - j * 6);
else
j--;
}
// Add the bytes
dArr[d++] = (byte) (i >> 16);
if (d < len) {
dArr[d++]= (byte) (i >> 8);
if (d < len)
dArr[d++] = (byte) i;
}
}
return dArr;
}
/** Decodes a BASE64 encoded string that is known to be resonably well formatted. The method is about twice as
* fast as {@link #decode(String)}. The preconditions are:<br>
* + The array must have a line length of 76 chars OR no line separators at all (one line).<br>
* + Line separator must be "\r\n", as specified in RFC 2045
* + The array must not contain illegal characters within the encoded string<br>
* + The array CAN have illegal characters at the beginning and end, those will be dealt with appropriately.<br>
* @param s The source string. Length 0 will return an empty array. <code>null</code> will throw an exception.
* @return The decoded array of bytes. May be of length 0.
*/
public final static byte[] decodeFast(String s)
{
// Check special case
int sLen = s.length();
if (sLen == 0)
return new byte[0];
int sIx = 0, eIx = sLen - 1; // Start and end index after trimming.
// Trim illegal chars from start
while (sIx < eIx && IA[s.charAt(sIx) & 0xff] < 0)
sIx++;
// Trim illegal chars from end
while (eIx > 0 && IA[s.charAt(eIx) & 0xff] < 0)
eIx--;
// get the padding count (=) (0, 1 or 2)
int pad = s.charAt(eIx) == '=' ? (s.charAt(eIx - 1) == '=' ? 2 : 1) : 0; // Count '=' at end.
int cCnt = eIx - sIx + 1; // Content count including possible separators
int sepCnt = sLen > 76 ? (s.charAt(76) == '\r' ? cCnt / 78 : 0) << 1 : 0;
int len = ((cCnt - sepCnt) * 6 >> 3) - pad; // The number of decoded bytes
byte[] dArr = new byte[len]; // Preallocate byte[] of exact length
// Decode all but the last 0 - 2 bytes.
int d = 0;
for (int cc = 0, eLen = (len / 3) * 3; d < eLen;) {
// Assemble three bytes into an int from four "valid" characters.
int i = IA[s.charAt(sIx++)] << 18 | IA[s.charAt(sIx++)] << 12 | IA[s.charAt(sIx++)] << 6 | IA[s.charAt(sIx++)];
// Add the bytes
dArr[d++] = (byte) (i >> 16);
dArr[d++] = (byte) (i >> 8);
dArr[d++] = (byte) i;
// If line separator, jump over it.
if (sepCnt > 0 && ++cc == 19) {
sIx += 2;
cc = 0;
}
}
if (d < len) {
// Decode last 1-3 bytes (incl '=') into 1-3 bytes
int i = 0;
for (int j = 0; sIx <= eIx - pad; j++)
i |= IA[s.charAt(sIx++)] << (18 - j * 6);
for (int r = 16; d < len; r -= 8)
dArr[d++] = (byte) (i >> r);
}
return dArr;
}
}
测试
TestBase64.java
package testBase64;
import java.io.UnsupportedEncodingException;
public class TestBase64 {
public static void main(String[] args) {
String str = "你们好~\n 你好！";
char[] encodedCharArray = null;
try {
encodedCharArray = Base64.encodeToChar(str.getBytes("UTF-8"), true);
System.out.println(encodedCharArray);
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
//从charArray转化为utf-8的字符串
byte[] bytes = Base64.decode(encodedCharArray);
try {
System.out.println(new String(bytes, "utf-8"));
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
}
}
输出：
可以看到第一行结束符号一个“=”就说明mod 3 = 2