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Editor to share with you how to use the Java language to achieve Base64 coding, I hope you will learn something after reading this article, let's discuss it together!

Import java.io.*

Public class MIMEBase64 {

/ *

This is a simple Base64 coding program.

Author: Roc Chen rocanny@163.com

Base64 uses 65 characters from a subset of US-ASCII, each represented by 6 bits

So the Base64 value of "m" is 38 and the binary form is 100110.

For text strings, the encoding process is as follows. For example, "men":

First convert to the US-ASCII value.

"m" decimal 109

"e" decimal 101

"n" decimal 110

Binary:

M 01101101

E 01100101

N 01101110

The three eight bits add up to 24 bits.

011011010110010101101110

And then divided into four six digits.

011011 010110 010101 101110

Now you get four values, in decimal

27 22 21 46

The corresponding Base64 characters are:

B W V u

The encoding is always based on 3 characters, resulting in 4 Base64 characters.

If there are only 1 or 2 characters left, use the special character "=" to complete the 4 words of Base64.

For example, encode "me"

01101101 01100101

0110110101100101

011011 010110 0101

111111 (and, make up 6 digits)

011011 010110 010100

B W U

B W U = ("=" complement 4 characters)

So "bWU=" is the base 64 value of "me".

Another example is the code "m"

01101101

011011 01

111111

011011 010000

B Q = =

So "bQ==" is the Base64 value of "m".

It is worth noting that MIME specifies a maximum of 76 characters per line.

, /

Static String BaseTable [] = {

"A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P"

"Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z", "a", "b", "c", "d", "e", "f"

"g", "h", "I", "j", "k", "l", "m", "n", "o", "p", "Q", "r", "s", "t", "u", "v"

"w", "x", "y", "z", "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "+", "/"

}

Public static void encode (String filename, BufferedWriter out) {

Try {

File f = new File (filename)

FileInputStream fin = new FileInputStream (filename)

/ / read the file to the BYTE array

Byte bytes [] = new byte [(int) (f.length ())]

Int n = fin.read (bytes)

If (n)

< 1) return; // 没有内容 byte buf[] = new byte[4]; // base64 字符数组 int n3byt = n / 3; // 3 bytes 组数 int nrest = n % 3; // 分组后剩余 bytes int k = n3byt * 3; // int linelength = 0; // 行长 int i = 0; // 指针 // 3-bytes 分组 ... while ( i < k ) { buf[0] = (byte)(( bytes[i] & 0xFC) >

> 2)

Buf [1] = (byte) ((Bytes [I] & 0x03) > 4))

Buf [2] = (byte) ((Bytes [I + 1] & 0x0F) > 6))

Buf [3] = (byte) (bytes [iTunes 2] & 0x3F)

Send (out, BaseTable [buf [0]])

Send (out, BaseTable [buf [1]])

Send (out, BaseTable [buf [2]])

Send (out, BaseTable [buf [3]])

/ *

The above code can be optimized, but it will be difficult to understand

Buf [0] = (byte) (b [I] > > 2)

Buf [1] = (byte) (b [I] & 0x03) > 4))

Buf [2] = (byte) (b [I + 1] & 0x0F) > 6))

Buf [3] = (byte) (b [I + 2] & 0x3F)

Send (out,BaseTable [buf [0]]) + BaseTable [buf [1]] +

BaseTable [buf [2]] + BaseTable [buf [3]])

, /

If ((linelength + = 4) > = 76) {

Send (out, "")

Linelength = 0

}

I + = 3

}

/ / handle the tail.

If (nrest==2) {

/ / 2 bytes left

Buf [0] = (byte) ((bytes [k] & 0xFC) > > 2)

Buf [1] = (byte) ((Bytes [k] & 0x03) > 4))

Buf [2] = (byte) ((bytes [knot 1] & 0x0F) > 2)

Buf [1] = (byte) ((bytes [k] & 0x03) 0) {

/ / send tail

If ((linelength + = 4) > = 76) send (out, ")

Send (out, BaseTable [buf [0]])

Send (out, BaseTable [buf [1]])

/ /

If (nrest==2) {

Send (out, BaseTable [buf [2]])

}

Else {

Send (out, "=")

}

Send (out, "=")

}

Out.flush ()

/ / the send method used here, please write it yourself according to your needs. It can be to output the results to the console, or to send an email.

}

Catch (Exception e) {

E.printStackTrace ()

}

}

}

After reading this article, I believe you have a certain understanding of "how to implement Base64 coding in Java language". If you want to know more about it, you are welcome to follow the industry information channel. Thank you for reading!

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