Below is java class that does Base 64 encoding.

public class Base64 {

private static final String base64code = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+ "abcdefghijklmnopqrstuvwxyz" + "0123456789" + "+/";

private static final int splitLinesAt = 76;

public static byte[] zeroPad(int length, byte[] bytes) {
byte[] padded = new byte[length]; // initialized to zero by JVM
System.arraycopy(bytes, 0, padded, 0, bytes.length);
return padded;
}

public static String encode(String string) {

String encoded = "";
byte[] stringArray;
try {
stringArray = string.getBytes("UTF-8"); // use appropriate encoding string!
} catch (Exception ignored) {
stringArray = string.getBytes(); // use locale default rather than croak
}
// determine how many padding bytes to add to the output
int paddingCount = (3 - (stringArray.length % 3)) % 3;
// add any necessary padding to the input
stringArray = zeroPad(stringArray.length + paddingCount, stringArray);
// process 3 bytes at a time, churning out 4 output bytes
// worry about CRLF insertions later
for (int i = 0; i < stringArray.length; i += 3) {
int j = ((stringArray[i] & 0xff) << 16) +
((stringArray[i + 1] & 0xff) << 8) +
(stringArray[i + 2] & 0xff);
encoded = encoded + base64code.charAt((j >> 18) & 0x3f) +
base64code.charAt((j >> 12) & 0x3f) +
base64code.charAt((j >> 6) & 0x3f) +
base64code.charAt(j & 0x3f);
}
// replace encoded padding nulls with "="
return splitLines(encoded.substring(0, encoded.length() -
paddingCount) + "==".substring(0, paddingCount));

}
public static String splitLines(String string) {

String lines = "";
for (int i = 0; i < string.length(); i += splitLinesAt) {

lines += string.substring(i, Math.min(string.length(), i + splitLinesAt));
lines += "\r\n";

}
return lines;

}
/* public static void main(String[] args) {

for (int i = 0; i < args.length; i++) {

System.err.println("encoding \"" + args[i] + "\"");
System.out.println("007 is now "+encode("007"));

}

} */

}

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How to use it?
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1. 1) Copy above code.
2. 2) Paste it in a .java file with name "Base64" .
   
3. 3) Import above class in java file where you you would like to use Base64 encoding.
4. 4) use, String encoded_string = Base64.encode("any string");
5. 5) encoded_string contains your encoded string.