Base64内容传送编码被设计用来把任意序列的8位字节描述为一种不易被人直接识别的形式。（The Base64 Content-Transfer-Encoding is designed to represent arbitrary sequences of octets in a form that need not be humanly readable.）
Base64是网络上最常见的用于传输8Bit字节代码的编码方式之一，在发送电子邮件时，服务器认证的用户名和密码需要用Base64编码，附件也需要用Base64编码……
下面是以前扒来的MD5算法的JAVA版本，J2ME可以放心使用。
package hlib;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Vector;
public class HBase64 ...{
private static final char[] legalChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
.toCharArray();
private static Vector nodes = new Vector();
public static String[] split(String original, String separator) ...{
nodes.removeAllElements(); // Parse nodes into vector
int index = original.indexOf(separator);
while (index >= 0) ...{
nodes.addElement(original.substring(0, index));
original = original.substring(index + separator.length());
index = original.indexOf(separator);
}
// Get the last node
nodes.addElement(original);
String[] result = new String[nodes.size()];
if (nodes.size() > 0) ...{
for (int loop = 0; loop < nodes.size(); loop++)
result[loop] = (String) nodes.elementAt(loop);
}
return result;
}
public static String replace(String s, String f, String r) ...{
if (s == null) return s;
if (f == null) return s;
if (r == null) r = "";
int index01 = s.indexOf(f);
while (index01 != -1) ...{
s = s.substring(0, index01) + r + s.substring(index01 + f.length());
index01 += r.length();
index01 = s.indexOf(f, index01);
}
return s;
}
public static String removeHtml(String text) ...{
try ...{
int idx = text.indexOf("<");
if (idx == -1) return text;
String plainText = "";
String htmlText = text;
int htmlStartIndex = htmlText.indexOf("<", 0);
if (htmlStartIndex == -1) ...{
return text;
}
while (htmlStartIndex >= 0) ...{
plainText += htmlText.substring(0, htmlStartIndex);
int htmlEndIndex = htmlText.indexOf(">", htmlStartIndex);
htmlText = htmlText.substring(htmlEndIndex + 1);
htmlStartIndex = htmlText.indexOf("<", 0);
}
plainText = plainText.trim();
return plainText;
} catch (Exception e) ...{
System.err.println("Error while removing HTML: " + e.toString());
return text;
}
}
/**//** Base64 encode the given data */
public static String encode(byte[] data) ...{
int start = 0;
int len = data.length;
StringBuffer buf = new StringBuffer(data.length * 3 / 2);
int end = len - 3;
int i = start;
int n = 0;
while (i <= end) ...{
int d = ((((int) data) & 0x0ff) << 16)
| ((((int) data[i + 1]) & 0x0ff) << 8)
| (((int) data[i + 2]) & 0x0ff);
buf.append(legalChars[(d >> 18) & 63]);
buf.append(legalChars[(d >> 12) & 63]);
buf.append(legalChars[(d >> 6) & 63]);
buf.append(legalChars[d & 63]);
i += 3;
if (n++ >= 14) ...{
n = 0;
buf.append(" ");
}
}
if (i == start + len - 2) ...{
int d = ((((int) data) & 0x0ff) << 16)
| ((((int) data[i + 1]) & 255) << 8);
buf.append(legalChars[(d >> 18) & 63]);
buf.append(legalChars[(d >> 12) & 63]);
buf.append(legalChars[(d >> 6) & 63]);
buf.append("=");
} else if (i == start + len - 1) ...{
int d = (((int) data) & 0x0ff) << 16;
buf.append(legalChars[(d >> 18) & 63]);
buf.append(legalChars[(d >> 12) & 63]);
buf.append("==");
}
return buf.toString();
}
private static int decode(char c) ...{
if (c >= 'A' && c <= 'Z')
return ((int) c) - 65;
else if (c >= 'a' && c <= 'z')
return ((int) c) - 97 + 26;
else if (c >= '0' && c <= '9')
return ((int) c) - 48 + 26 + 26;
else
switch (c) ...{
case '+':
return 62;
case '/':
return 63;
case '=':
return 0;
default:
throw new RuntimeException("unexpected code: " + c);
}
}
/**//** * Decodes the given Base64 encoded String to a new byte array. The byte * array holding the decoded data is returned. */
public static byte[] decode(String s) ...{
ByteArrayOutputStream bos = new ByteArrayOutputStream();
try ...{
decode(s, bos);
} catch (IOException e) ...{
throw new RuntimeException();
}
byte[] decodedBytes = bos.toByteArray();
try ...{
bos.close();
bos = null;
} catch (IOException ex) ...{
System.err.println("Error while decoding BASE64: " + ex.toString());
}
return decodedBytes;
}
private static void decode(String s, OutputStream os) throws IOException ...{
int i = 0;
int len = s.length();
while (true) ...{
while (i < len && s.charAt(i) <= ' ')
i++;
if (i == len) break;
int tri = (decode(s.charAt(i)) << 18)
+ (decode(s.charAt(i + 1)) << 12)
+ (decode(s.charAt(i + 2)) << 6)
+ (decode(s.charAt(i + 3)));
os.write((tri >> 16) & 255);
if (s.charAt(i + 2) == '=') break;
os.write((tri >> 8) & 255);
if (s.charAt(i + 3) == '=') break;
os.write(tri & 255);
i += 4;
}
}
}
