一道java编程题…… 编写程序实现将BASE64编码和解码功能,将UNICODE字符串“中国”编码为BASE64格式的数据,并解码。基本不懂~求高手解答~ 解决方案 » 免费领取超大流量手机卡,每月29元包185G流量+100分钟通话, 中国电信官方发货 sun.misc.BASE64Decodersun.misc.BASE64Encoder 有实现好了的。 public class Base64 { private static final byte[] encodingTable = { (byte) 'A', (byte) 'B', (byte) 'C', (byte) 'D', (byte) 'E', (byte) 'F', (byte) 'G', (byte) 'H', (byte) 'I', (byte) 'J', (byte) 'K', (byte) 'L', (byte) 'M', (byte) 'N', (byte) 'O', (byte) 'P', (byte) 'Q', (byte) 'R', (byte) 'S', (byte) 'T', (byte) 'U', (byte) 'V', (byte) 'W', (byte) 'X', (byte) 'Y', (byte) 'Z', (byte) 'a', (byte) 'b', (byte) 'c', (byte) 'd', (byte) 'e', (byte) 'f', (byte) 'g', (byte) 'h', (byte) 'i', (byte) 'j', (byte) 'k', (byte) 'l', (byte) 'm', (byte) 'n', (byte) 'o', (byte) 'p', (byte) 'q', (byte) 'r', (byte) 's', (byte) 't', (byte) 'u', (byte) 'v', (byte) 'w', (byte) 'x', (byte) 'y', (byte) 'z', (byte) '0', (byte) '1', (byte) '2', (byte) '3', (byte) '4', (byte) '5', (byte) '6', (byte) '7', (byte) '8', (byte) '9', (byte) '+', (byte) '/' }; private static final byte[] decodingTable; static { decodingTable = new byte[128]; for (int i = 0; i < 128; i++) { decodingTable[i] = (byte) -1; } for (int i = 'A'; i <= 'Z'; i++) { decodingTable[i] = (byte) (i - 'A'); } for (int i = 'a'; i <= 'z'; i++) { decodingTable[i] = (byte) (i - 'a' + 26); } for (int i = '0'; i <= '9'; i++) { decodingTable[i] = (byte) (i - '0' + 52); } decodingTable['+'] = 62; decodingTable['/'] = 63; } public static byte[] encode(byte[] data) { byte[] bytes; int modulus = data.length % 3; if (modulus == 0) { bytes = new byte[(4 * data.length) / 3]; } else { bytes = new byte[4 * ((data.length / 3) + 1)]; } int dataLength = (data.length - modulus); int a1; int a2; int a3; for (int i = 0, j = 0; i < dataLength; i += 3, j += 4) { a1 = data[i] & 0xff; a2 = data[i + 1] & 0xff; a3 = data[i + 2] & 0xff; bytes[j] = encodingTable[(a1 >>> 2) & 0x3f]; bytes[j + 1] = encodingTable[((a1 << 4) | (a2 >>> 4)) & 0x3f]; bytes[j + 2] = encodingTable[((a2 << 2) | (a3 >>> 6)) & 0x3f]; bytes[j + 3] = encodingTable[a3 & 0x3f]; } int b1; int b2; int b3; int d1; int d2; switch (modulus) { case 0: /* nothing left to do */ break; case 1: d1 = data[data.length - 1] & 0xff; b1 = (d1 >>> 2) & 0x3f; b2 = (d1 << 4) & 0x3f; bytes[bytes.length - 4] = encodingTable[b1]; bytes[bytes.length - 3] = encodingTable[b2]; bytes[bytes.length - 2] = (byte) '='; bytes[bytes.length - 1] = (byte) '='; break; case 2: d1 = data[data.length - 2] & 0xff; d2 = data[data.length - 1] & 0xff; b1 = (d1 >>> 2) & 0x3f; b2 = ((d1 << 4) | (d2 >>> 4)) & 0x3f; b3 = (d2 << 2) & 0x3f; bytes[bytes.length - 4] = encodingTable[b1]; bytes[bytes.length - 3] = encodingTable[b2]; bytes[bytes.length - 2] = encodingTable[b3]; bytes[bytes.length - 1] = (byte) '='; break; } return bytes; } public static byte[] decode(byte[] data) { byte[] bytes; byte b1; byte b2; byte b3; byte b4; data = discardNonBase64Bytes(data); if (data[data.length - 2] == '=') { bytes = new byte[(((data.length / 4) - 1) * 3) + 1]; } else if (data[data.length - 1] == '=') { bytes = new byte[(((data.length / 4) - 1) * 3) + 2]; } else { bytes = new byte[((data.length / 4) * 3)]; } for (int i = 0, j = 0; i < (data.length - 4); i += 4, j += 3) { b1 = decodingTable[data[i]]; b2 = decodingTable[data[i + 1]]; b3 = decodingTable[data[i + 2]]; b4 = decodingTable[data[i + 3]]; bytes[j] = (byte) ((b1 << 2) | (b2 >> 4)); bytes[j + 1] = (byte) ((b2 << 4) | (b3 >> 2)); bytes[j + 2] = (byte) ((b3 << 6) | b4); } if (data[data.length - 2] == '=') { b1 = decodingTable[data[data.length - 4]]; b2 = decodingTable[data[data.length - 3]]; bytes[bytes.length - 1] = (byte) ((b1 << 2) | (b2 >> 4)); } else if (data[data.length - 1] == '=') { b1 = decodingTable[data[data.length - 4]]; b2 = decodingTable[data[data.length - 3]]; b3 = decodingTable[data[data.length - 2]]; bytes[bytes.length - 2] = (byte) ((b1 << 2) | (b2 >> 4)); bytes[bytes.length - 1] = (byte) ((b2 << 4) | (b3 >> 2)); } else { b1 = decodingTable[data[data.length - 4]]; b2 = decodingTable[data[data.length - 3]]; b3 = decodingTable[data[data.length - 2]]; b4 = decodingTable[data[data.length - 1]]; bytes[bytes.length - 3] = (byte) ((b1 << 2) | (b2 >> 4)); bytes[bytes.length - 2] = (byte) ((b2 << 4) | (b3 >> 2)); bytes[bytes.length - 1] = (byte) ((b3 << 6) | b4); } return bytes; } public static byte[] decode(String data) { byte[] bytes; byte b1; byte b2; byte b3; byte b4; data = discardNonBase64Chars(data); if (data.charAt(data.length() - 2) == '=') { bytes = new byte[(((data.length() / 4) - 1) * 3) + 1]; } else if (data.charAt(data.length() - 1) == '=') { bytes = new byte[(((data.length() / 4) - 1) * 3) + 2]; } else { bytes = new byte[((data.length() / 4) * 3)]; } for (int i = 0, j = 0; i < (data.length() - 4); i += 4, j += 3) { b1 = decodingTable[data.charAt(i)]; b2 = decodingTable[data.charAt(i + 1)]; b3 = decodingTable[data.charAt(i + 2)]; b4 = decodingTable[data.charAt(i + 3)]; bytes[j] = (byte) ((b1 << 2) | (b2 >> 4)); bytes[j + 1] = (byte) ((b2 << 4) | (b3 >> 2)); bytes[j + 2] = (byte) ((b3 << 6) | b4); } if (data.charAt(data.length() - 2) == '=') { b1 = decodingTable[data.charAt(data.length() - 4)]; b2 = decodingTable[data.charAt(data.length() - 3)]; bytes[bytes.length - 1] = (byte) ((b1 << 2) | (b2 >> 4)); } else if (data.charAt(data.length() - 1) == '=') { b1 = decodingTable[data.charAt(data.length() - 4)]; b2 = decodingTable[data.charAt(data.length() - 3)]; b3 = decodingTable[data.charAt(data.length() - 2)]; bytes[bytes.length - 2] = (byte) ((b1 << 2) | (b2 >> 4)); bytes[bytes.length - 1] = (byte) ((b2 << 4) | (b3 >> 2)); } else { b1 = decodingTable[data.charAt(data.length() - 4)]; b2 = decodingTable[data.charAt(data.length() - 3)]; b3 = decodingTable[data.charAt(data.length() - 2)]; b4 = decodingTable[data.charAt(data.length() - 1)]; bytes[bytes.length - 3] = (byte) ((b1 << 2) | (b2 >> 4)); bytes[bytes.length - 2] = (byte) ((b2 << 4) | (b3 >> 2)); bytes[bytes.length - 1] = (byte) ((b3 << 6) | b4); } return bytes; } private static byte[] discardNonBase64Bytes(byte[] data) { byte[] temp = new byte[data.length]; int bytesCopied = 0; for (int i = 0; i < data.length; i++) { if (isValidBase64Byte(data[i])) { temp[bytesCopied++] = data[i]; } } byte[] newData = new byte[bytesCopied]; System.arraycopy(temp, 0, newData, 0, bytesCopied); return newData; } private static String discardNonBase64Chars(String data) { StringBuffer sb = new StringBuffer(); int length = data.length(); for (int i = 0; i < length; i++) { if (isValidBase64Byte((byte) (data.charAt(i)))) { sb.append(data.charAt(i)); } } return sb.toString(); } private static boolean isValidBase64Byte(byte b) { if (b == '=') { return true; } else if ((b < 0) || (b >= 128)) { return false; } else if (decodingTable[b] == -1) { return false; } return true; } public static void main(String[] args) { String data = "中国"; byte[] result = Base64.encode(data.getBytes()); System.out.println(data); System.out.println(new String(result)); System.out.println(new String(Base64.decode(new String(result)))); }}自己百度下谷歌下 有很多的 public class Base64Util { /** * 将 s 进行 BASE64 编码 * * @param s * @return */ public static String getBASE64(String s) { if (s == null) { return null; } return (new sun.misc.BASE64Encoder()).encode(s.getBytes()); } /** * 将 BASE64 编码的字符串 s 进行解码 * * @param s * @return */ public static String getFromBASE64(String s) { if (s == null) { return null; } BASE64Decoder decoder = new BASE64Decoder(); try { byte[] b = decoder.decodeBuffer(s); return new String(b); } catch (Exception e) { return null; } } public static void main(String args[]) { String str = "我的测试字符串"; System.out.println("原字符串:" + str); String encodeStr = Base64Util.getBASE64(str); System.out.println("编码后:" + encodeStr); String decodeStr = Base64Util.getFromBASE64(encodeStr); System.out.println("解码后:" + decodeStr); }}不过使用sum的类不是太好~ 正则表达式的疑惑 如何形成以下数组并打印出来? 看到了java编的桌面软件,散分 急!!为什么不实现接口所有的方法也可以使用该接口? 数字的分割 请教~~当鼠标经过HTML的表格td时..... 求助+感谢csdn上的朋友+最近自己大学生活的感想 有句语法不太清楚 java7,8 System.out.println问题 关于java中Int等类型装箱时发生的奇怪现象 java swing 键盘响应问题 BigInteger
sun.misc.BASE64Encoder 有实现好了的。
public class Base64 {
private static final byte[] encodingTable = {
(byte) 'A', (byte) 'B', (byte) 'C', (byte) 'D', (byte) 'E',
(byte) 'F', (byte) 'G', (byte) 'H', (byte) 'I', (byte) 'J',
(byte) 'K', (byte) 'L', (byte) 'M', (byte) 'N', (byte) 'O',
(byte) 'P', (byte) 'Q', (byte) 'R', (byte) 'S', (byte) 'T',
(byte) 'U', (byte) 'V', (byte) 'W', (byte) 'X', (byte) 'Y',
(byte) 'Z', (byte) 'a', (byte) 'b', (byte) 'c', (byte) 'd',
(byte) 'e', (byte) 'f', (byte) 'g', (byte) 'h', (byte) 'i',
(byte) 'j', (byte) 'k', (byte) 'l', (byte) 'm', (byte) 'n',
(byte) 'o', (byte) 'p', (byte) 'q', (byte) 'r', (byte) 's',
(byte) 't', (byte) 'u', (byte) 'v', (byte) 'w', (byte) 'x',
(byte) 'y', (byte) 'z', (byte) '0', (byte) '1', (byte) '2',
(byte) '3', (byte) '4', (byte) '5', (byte) '6', (byte) '7',
(byte) '8', (byte) '9', (byte) '+', (byte) '/'
};
private static final byte[] decodingTable;
static {
decodingTable = new byte[128];
for (int i = 0; i < 128; i++) {
decodingTable[i] = (byte) -1;
}
for (int i = 'A'; i <= 'Z'; i++) {
decodingTable[i] = (byte) (i - 'A');
}
for (int i = 'a'; i <= 'z'; i++) {
decodingTable[i] = (byte) (i - 'a' + 26);
}
for (int i = '0'; i <= '9'; i++) {
decodingTable[i] = (byte) (i - '0' + 52);
}
decodingTable['+'] = 62;
decodingTable['/'] = 63;
}
public static byte[] encode(byte[] data) {
byte[] bytes;
int modulus = data.length % 3;
if (modulus == 0) {
bytes = new byte[(4 * data.length) / 3];
} else {
bytes = new byte[4 * ((data.length / 3) + 1)];
}
int dataLength = (data.length - modulus);
int a1;
int a2;
int a3;
for (int i = 0, j = 0; i < dataLength; i += 3, j += 4) {
a1 = data[i] & 0xff;
a2 = data[i + 1] & 0xff;
a3 = data[i + 2] & 0xff;
bytes[j] = encodingTable[(a1 >>> 2) & 0x3f];
bytes[j + 1] = encodingTable[((a1 << 4) | (a2 >>> 4)) & 0x3f];
bytes[j + 2] = encodingTable[((a2 << 2) | (a3 >>> 6)) & 0x3f];
bytes[j + 3] = encodingTable[a3 & 0x3f];
}
int b1;
int b2;
int b3;
int d1;
int d2;
switch (modulus) {
case 0: /* nothing left to do */
break;
case 1:
d1 = data[data.length - 1] & 0xff;
b1 = (d1 >>> 2) & 0x3f;
b2 = (d1 << 4) & 0x3f;
bytes[bytes.length - 4] = encodingTable[b1];
bytes[bytes.length - 3] = encodingTable[b2];
bytes[bytes.length - 2] = (byte) '=';
bytes[bytes.length - 1] = (byte) '=';
break;
case 2:
d1 = data[data.length - 2] & 0xff;
d2 = data[data.length - 1] & 0xff;
b1 = (d1 >>> 2) & 0x3f;
b2 = ((d1 << 4) | (d2 >>> 4)) & 0x3f;
b3 = (d2 << 2) & 0x3f;
bytes[bytes.length - 4] = encodingTable[b1];
bytes[bytes.length - 3] = encodingTable[b2];
bytes[bytes.length - 2] = encodingTable[b3];
bytes[bytes.length - 1] = (byte) '=';
break;
}
return bytes;
}
public static byte[] decode(byte[] data) {
byte[] bytes;
byte b1;
byte b2;
byte b3;
byte b4;
data = discardNonBase64Bytes(data);
if (data[data.length - 2] == '=') {
bytes = new byte[(((data.length / 4) - 1) * 3) + 1];
} else if (data[data.length - 1] == '=') {
bytes = new byte[(((data.length / 4) - 1) * 3) + 2];
} else {
bytes = new byte[((data.length / 4) * 3)];
}
for (int i = 0, j = 0; i < (data.length - 4); i += 4, j += 3) {
b1 = decodingTable[data[i]];
b2 = decodingTable[data[i + 1]];
b3 = decodingTable[data[i + 2]];
b4 = decodingTable[data[i + 3]];
bytes[j] = (byte) ((b1 << 2) | (b2 >> 4));
bytes[j + 1] = (byte) ((b2 << 4) | (b3 >> 2));
bytes[j + 2] = (byte) ((b3 << 6) | b4);
}
if (data[data.length - 2] == '=') {
b1 = decodingTable[data[data.length - 4]];
b2 = decodingTable[data[data.length - 3]];
bytes[bytes.length - 1] = (byte) ((b1 << 2) | (b2 >> 4));
} else if (data[data.length - 1] == '=') {
b1 = decodingTable[data[data.length - 4]];
b2 = decodingTable[data[data.length - 3]];
b3 = decodingTable[data[data.length - 2]];
bytes[bytes.length - 2] = (byte) ((b1 << 2) | (b2 >> 4));
bytes[bytes.length - 1] = (byte) ((b2 << 4) | (b3 >> 2));
} else {
b1 = decodingTable[data[data.length - 4]];
b2 = decodingTable[data[data.length - 3]];
b3 = decodingTable[data[data.length - 2]];
b4 = decodingTable[data[data.length - 1]];
bytes[bytes.length - 3] = (byte) ((b1 << 2) | (b2 >> 4));
bytes[bytes.length - 2] = (byte) ((b2 << 4) | (b3 >> 2));
bytes[bytes.length - 1] = (byte) ((b3 << 6) | b4);
}
return bytes;
}
public static byte[] decode(String data) {
byte[] bytes;
byte b1;
byte b2;
byte b3;
byte b4;
data = discardNonBase64Chars(data);
if (data.charAt(data.length() - 2) == '=') {
bytes = new byte[(((data.length() / 4) - 1) * 3) + 1];
} else if (data.charAt(data.length() - 1) == '=') {
bytes = new byte[(((data.length() / 4) - 1) * 3) + 2];
} else {
bytes = new byte[((data.length() / 4) * 3)];
}
for (int i = 0, j = 0; i < (data.length() - 4); i += 4, j += 3) {
b1 = decodingTable[data.charAt(i)];
b2 = decodingTable[data.charAt(i + 1)];
b3 = decodingTable[data.charAt(i + 2)];
b4 = decodingTable[data.charAt(i + 3)];
bytes[j] = (byte) ((b1 << 2) | (b2 >> 4));
bytes[j + 1] = (byte) ((b2 << 4) | (b3 >> 2));
bytes[j + 2] = (byte) ((b3 << 6) | b4);
}
if (data.charAt(data.length() - 2) == '=') {
b1 = decodingTable[data.charAt(data.length() - 4)];
b2 = decodingTable[data.charAt(data.length() - 3)];
bytes[bytes.length - 1] = (byte) ((b1 << 2) | (b2 >> 4));
} else if (data.charAt(data.length() - 1) == '=') {
b1 = decodingTable[data.charAt(data.length() - 4)];
b2 = decodingTable[data.charAt(data.length() - 3)];
b3 = decodingTable[data.charAt(data.length() - 2)];
bytes[bytes.length - 2] = (byte) ((b1 << 2) | (b2 >> 4));
bytes[bytes.length - 1] = (byte) ((b2 << 4) | (b3 >> 2));
} else {
b1 = decodingTable[data.charAt(data.length() - 4)];
b2 = decodingTable[data.charAt(data.length() - 3)];
b3 = decodingTable[data.charAt(data.length() - 2)];
b4 = decodingTable[data.charAt(data.length() - 1)];
bytes[bytes.length - 3] = (byte) ((b1 << 2) | (b2 >> 4));
bytes[bytes.length - 2] = (byte) ((b2 << 4) | (b3 >> 2));
bytes[bytes.length - 1] = (byte) ((b3 << 6) | b4);
}
return bytes;
}
private static byte[] discardNonBase64Bytes(byte[] data) {
byte[] temp = new byte[data.length];
int bytesCopied = 0;
for (int i = 0; i < data.length; i++) {
if (isValidBase64Byte(data[i])) {
temp[bytesCopied++] = data[i];
}
}
byte[] newData = new byte[bytesCopied];
System.arraycopy(temp, 0, newData, 0, bytesCopied);
return newData;
}
private static String discardNonBase64Chars(String data) {
StringBuffer sb = new StringBuffer();
int length = data.length();
for (int i = 0; i < length; i++) {
if (isValidBase64Byte((byte) (data.charAt(i)))) {
sb.append(data.charAt(i));
}
}
return sb.toString();
}
private static boolean isValidBase64Byte(byte b) {
if (b == '=') {
return true;
} else if ((b < 0) || (b >= 128)) {
return false;
} else if (decodingTable[b] == -1) {
return false;
}
return true;
}
public static void main(String[] args) {
String data = "中国";
byte[] result = Base64.encode(data.getBytes());
System.out.println(data);
System.out.println(new String(result));
System.out.println(new String(Base64.decode(new String(result))));
}
}
自己百度下谷歌下 有很多的
public class Base64Util {
/**
* 将 s 进行 BASE64 编码
*
* @param s
* @return
*/
public static String getBASE64(String s) {
if (s == null) {
return null;
} return (new sun.misc.BASE64Encoder()).encode(s.getBytes());
} /**
* 将 BASE64 编码的字符串 s 进行解码
*
* @param s
* @return
*/
public static String getFromBASE64(String s) {
if (s == null) {
return null;
} BASE64Decoder decoder = new BASE64Decoder();
try {
byte[] b = decoder.decodeBuffer(s);
return new String(b);
} catch (Exception e) {
return null;
}
} public static void main(String args[]) {
String str = "我的测试字符串";
System.out.println("原字符串:" + str);
String encodeStr = Base64Util.getBASE64(str);
System.out.println("编码后:" + encodeStr);
String decodeStr = Base64Util.getFromBASE64(encodeStr);
System.out.println("解码后:" + decodeStr);
}
}不过使用sum的类不是太好~