前几天无意中看到Java中有Base64编码，不解的我去百科了一下，了解了Base64的基本使用和实现原理，于是在空暇时自己手动写了一个，这个类可以完成对字母数字的编码和解码工作，但是对于中文，还没有仔细研究其编码的实现过程。至于什么是Base64，用它来干什么，请移步到：http://zh.wikipedia.org/zh-cn/Base64
下面贴出这个工具类的源代码，供朋友们参考，本人新手写得不好，请用力拍砖：
/************************Base64Util.java*****************************/
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package util;
import java.util.HashMap;
import java.util.Map;
/** * This class is a tool class to convert Base64 string and
* normal string to each other. <br><br>
* More information about base64, Please refer to:
* http://zh.wikipedia.org/zh-cn/Base64
* @author user
*/
public class Base64Util {
private static final Map<Integer, Character> base64CharMap = new HashMap<>();
private static final String base64CharString =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
static {
// initialize base64 map
for (int i=0;i<base64CharString.length();i++){
char c = base64CharString.charAt(i);
base64CharMap.put(new Integer(i), new Character(c));
} } /**
* This method is used to encode a normal string to base64 string * @param origin * The String to be encoded * @return * The String after encoded. */ public static String encode (String origin) {
if (origin == null) {
return null;
} if (origin.length() == 0) {
return "";
} int length = origin.length();
String binaryString = "";
// to binary String
for (int i=0;i<length;i++) {
int ascii = origin.charAt(i);
String binaryCharString = Integer.toBinaryString(ascii); while (binaryCharString.length() < 8) {
binaryCharString = "0" + binaryCharString;
} binaryString += binaryCharString; } // to base64 index
int beginIndex = 0;
int endIndex = beginIndex + 6;
String base64BinaryString = "";
String charString = "";
while ((base64BinaryString =
binaryString.substring(beginIndex, endIndex)).length() > 0) {
//if length is less than 6, add "0".
while (base64BinaryString.length() < 6) {
base64BinaryString += "0";
} int index = Integer.parseInt(base64BinaryString, 2);
char base64Char = base64CharMap.get(index);
charString = charString + base64Char; beginIndex += 6;
endIndex += 6;
if (endIndex >= binaryString.length()) {
endIndex = binaryString.length(); } if (endIndex < beginIndex) {
break;
} } if (length % 3 == 2) {
charString += "=";
} if (length % 3 == 1) {
charString += "==";
} return charString;
} /**
* This method is used to decode from base64 string to a normal string. * @param encodedString * The string to be decoded. * @return * The string after decoded. */ public static String decode(String encodedString) {
if (encodedString == null) {
return null;
} if (encodedString.length() == 0) {
return "";
} //get origin base64 String
String origin = encodedString.substring(0,encodedString.indexOf("="));
String equals = encodedString.substring(encodedString.indexOf("="));
String binaryString = "";
//convert base64 string to binary string
for (int i=0;i<origin.length();i++) {
char c = origin.charAt(i);
int ascii = base64CharString.indexOf(c);
String binaryCharString = Integer.toBinaryString(ascii); while (binaryCharString.length() < 6) {
binaryCharString = "0" + binaryCharString;
} binaryString += binaryCharString; } // the encoded string has 1 "=", means that the binary string has append 2 "0"
if (equals.length() == 1) {
binaryString = binaryString.substring(0,binaryString.length()-2);
} // the encoded string has 2 "=", means that the binary string has append 4 "0"
if (equals.length() == 2) {
binaryString = binaryString.substring(0,binaryString.length()-4);
} // convert to String
String charString = "";
String resultString = "";
int beginIndex = 0;
int endIndex = beginIndex + 8;
while ((charString =
binaryString.substring(beginIndex, endIndex)).length() == 8) {
int ascii = Integer.parseInt(charString, 2);
resultString += (char)ascii;
beginIndex += 8;
endIndex += 8;
if (endIndex > binaryString.length()) {
break;
} } return resultString;
} // Test methods here.
public static void main(String[] args) {
String originString = "Man is distinguished, not only by his reason, but by this singular passion from other animals, which is a lust of the mind, that by a perseverance of delight in the continued and indefatigable generation of knowledge, exceeds the short vehemence of any carnal pleasure.";
String base64String = "TWFuIGlzIGRpc3Rpbmd1aXNoZWQsIG5vdCBvbmx5IGJ5IGhpcyByZWFzb24sIGJ1dCBieSB0aGlz" +
"IHNpbmd1bGFyIHBhc3Npb24gZnJvbSBvdGhlciBhbmltYWxzLCB3aGljaCBpcyBhIGx1c3Qgb2Yg" +
"dGhlIG1pbmQsIHRoYXQgYnkgYSBwZXJzZXZlcmFuY2Ugb2YgZGVsaWdodCBpbiB0aGUgY29udGlu" +
"dWVkIGFuZCBpbmRlZmF0aWdhYmxlIGdlbmVyYXRpb24gb2Yga25vd2xlZGdlLCBleGNlZWRzIHRo" +
"ZSBzaG9ydCB2ZWhlbWVuY2Ugb2YgYW55IGNhcm5hbCBwbGVhc3VyZS4=";
System.out.println("===============encode=================");
String result = encode(originString); System.out.println(result); System.out.println(result.equals(base64String)); System.out.println("===============decode=================");
String decodedString = decode(base64String); System.out.println(decodedString); System.out.println(originString.equals(decodedString)); System.out.println(decode(encode("abcdefg")));
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