blocks|key|1644166|text|特别是在Commons+Codec中:将Base64类设置为decode(byte[]+array)或encode(byte[]+array)|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1644167|entityMap|0|LINK|mutability|MUTABLE|url|http://commons.apache.org/codec/|1|http://commons.apache.org/codec/apidocs/org/apache/commons/codec/binary/Base64.html^0|K|6|U|K|1F|K|4|D|0|K|6|1|0^^$0|@$1|2|3|4|5|6|7|P|8|@$9|Q|A|R|B|C]|$9|S|A|T|B|C]|$9|U|A|V|B|C]]|D|@$9|W|A|X|1|Y]|$9|Z|A|10|1|11]]|E|$]]|$1|F|3|-4|5|6|7|12|8|@]|D|@]|E|$]]]|G|$H|$5|I|J|K|E|$L|M]]|N|$5|I|J|K|E|$L|O]]]]

Specifically in <a href="http://commons.apache.org/codec/" rel="noreferrer">Commons Codec</a>: class <a href="http://commons.apache.org/codec/apidocs/org/apache/commons/codec/binary/Base64.html" rel="noreferrer"><code>Base64</code></a> to <code>decode(byte[] array)</code> or <code>encode(byte[] array)</code>

blocks|key|1644220|text|作为sun.misc.BASE64Decoder或非核心库的替代方案，请看javax.mail.internet.MimeUtility.decode()。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1644221|public+static+byte[]+encode(byte[]+b)+throws+Exception+{
++++ByteArrayOutputStream+baos+=+new+ByteArrayOutputStream();
++++OutputStream+b64os+=+MimeUtility.encode(baos,+"base64");
++++b64os.write(b);
++++b64os.close();
++++return+baos.toByteArray();
}
public+static+byte[]+decode(byte[]+b)+throws+Exception+{
++++ByteArrayInputStream+bais+=+new+ByteArrayInputStream(b);
++++InputStream+b64is+=+MimeUtility.decode(bais,+"base64");
++++byte[]+tmp+=+new+byte[b.length];
++++int+n+=+b64is.read(tmp);
++++byte[]+res+=+new+byte[n];
++++System.arraycopy(tmp,+0,+res,+0,+n);
++++return+res;
}|code-block|syntax|javascript|1644222|完整代码链接：Encode/Decode+to/from+Base64|1644223|entityMap|0|LINK|mutability|MUTABLE|url|http://www.rgagnon.com/javadetails/java-0598.html^0|2|M|11|14|0|0|7|S|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|Z|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|10|8|@]|D|@$9|11|A|12|1|13]]|E|$]]|$1|M|3|-4|5|6|7|14|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]]]

As an alternative to <code>sun.misc.BASE64Decoder</code> or non-core libraries, look at <code>javax.mail.internet.MimeUtility.decode()</code>.

<pre><code>public static byte[] encode(byte[] b) throws Exception {
 ByteArrayOutputStream baos = new ByteArrayOutputStream();
 OutputStream b64os = MimeUtility.encode(baos, "base64");
 b64os.write(b);
 b64os.close();
 return baos.toByteArray();
}
public static byte[] decode(byte[] b) throws Exception {
 ByteArrayInputStream bais = new ByteArrayInputStream(b);
 InputStream b64is = MimeUtility.decode(bais, "base64");
 byte[] tmp = new byte[b.length];
 int n = b64is.read(tmp);
 byte[] res = new byte[n];
 System.arraycopy(tmp, 0, res, 0, n);
 return res;
}
</code></pre>

Link with full code: <a href="http://www.rgagnon.com/javadetails/java-0598.html" rel="nofollow noreferrer">Encode/Decode to/from Base64</a>

blocks|key|1644261|text|从v6开始，Java附带了JAXB。javax.xml.bind.DatatypeConverter的静态方法可以使这一切变得简单。参见parseBase64Binary()和printBase64Binary()。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1644262|entityMap|0|LINK|mutability|MUTABLE|url|http://download.oracle.com/javase/6/docs/api/javax/xml/bind/DatatypeConverter.html|1|http://download.oracle.com/javase/6/docs/api/javax/xml/bind/DatatypeConverter.html#parseBase64Binary(java.lang.String)|2|http://download.oracle.com/javase/6/docs/api/javax/xml/bind/DatatypeConverter.html#printBase64Binary%2528byte[]%2529^0|I|W|1W|J|2G|J|I|W|0|1W|J|1|2G|J|2|0^^$0|@$1|2|3|4|5|6|7|R|8|@$9|S|A|T|B|C]|$9|U|A|V|B|C]|$9|W|A|X|B|C]]|D|@$9|Y|A|Z|1|10]|$9|11|A|12|1|13]|$9|14|A|15|1|16]]|E|$]]|$1|F|3|-4|5|6|7|17|8|@]|D|@]|E|$]]]|G|$H|$5|I|J|K|E|$L|M]]|N|$5|I|J|K|E|$L|O]]|P|$5|I|J|K|E|$L|Q]]]]

As of v6, Java SE ships with JAXB. <a href="http://download.oracle.com/javase/6/docs/api/javax/xml/bind/DatatypeConverter.html" rel="noreferrer"><code>javax.xml.bind.DatatypeConverter</code></a> has static methods that make this easy. See <a href="http://download.oracle.com/javase/6/docs/api/javax/xml/bind/DatatypeConverter.html#parseBase64Binary(java.lang.String)" rel="noreferrer"><code>parseBase64Binary()</code></a> and <a href="http://download.oracle.com/javase/6/docs/api/javax/xml/bind/DatatypeConverter.html#printBase64Binary%28byte[]%29" rel="noreferrer"><code>printBase64Binary()</code></a>.

blocks|key|1429418|text|我的解决方案是最快最简单的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1429419|public+class+MyBase64+{

++++private+final+static+char[]+ALPHABET+=+"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789%2B/".toCharArray();

++++private+static+int[]++toInt+++=+new+int[128];

++++static+{
++++++++for(int+i=0;+i<+ALPHABET.length;+i%2B%2B){
++++++++++++toInt[ALPHABET[i]]=+i;
++++++++}
++++}

++++/**
+++++*+Translates+the+specified+byte+array+into+Base64+string.
+++++*
+++++*+@param+buf+the+byte+array+(not+null)
+++++*+@return+the+translated+Base64+string+(not+null)
+++++*/
++++public+static+String+encode(byte[]+buf){
++++++++int+size+=+buf.length;
++++++++char[]+ar+=+new+char[((size+%2B+2)+/+3)+*+4];
++++++++int+a+=+0;
++++++++int+i=0;
++++++++while(i+<+size){
++++++++++++byte+b0+=+buf[i%2B%2B];
++++++++++++byte+b1+=+(i+<+size)+?+buf[i%2B%2B]+:+0;
++++++++++++byte+b2+=+(i+<+size)+?+buf[i%2B%2B]+:+0;

++++++++++++int+mask+=+0x3F;
++++++++++++ar[a%2B%2B]+=+ALPHABET[(b0+>>+2)+&+mask];
++++++++++++ar[a%2B%2B]+=+ALPHABET[((b0+<<+4)+%7C+((b1+&+0xFF)+>>+4))+&+mask];
++++++++++++ar[a%2B%2B]+=+ALPHABET[((b1+<<+2)+%7C+((b2+&+0xFF)+>>+6))+&+mask];
++++++++++++ar[a%2B%2B]+=+ALPHABET[b2+&+mask];
++++++++}
++++++++switch(size+%25+3){
++++++++++++case+1:+ar[--a]++=+'=';
++++++++++++case+2:+ar[--a]++=+'=';
++++++++}
++++++++return+new+String(ar);
++++}

++++/**
+++++*+Translates+the+specified+Base64+string+into+a+byte+array.
+++++*
+++++*+@param+s+the+Base64+string+(not+null)
+++++*+@return+the+byte+array+(not+null)
+++++*/
++++public+static+byte[]+decode(String+s){
++++++++int+delta+=+s.endsWith(+"=="+)+?+2+:+s.endsWith(+"="+)+?+1+:+0;
++++++++byte[]+buffer+=+new+byte[s.length()*3/4+-+delta];
++++++++int+mask+=+0xFF;
++++++++int+index+=+0;
++++++++for(int+i=0;+i<+s.length();+i%2B=4){
++++++++++++int+c0+=+toInt[s.charAt(+i+)];
++++++++++++int+c1+=+toInt[s.charAt(+i+%2B+1)];
++++++++++++buffer[index%2B%2B]=+(byte)(((c0+<<+2)+%7C+(c1+>>+4))+&+mask);
++++++++++++if(index+>=+buffer.length){
++++++++++++++++return+buffer;
++++++++++++}
++++++++++++int+c2+=+toInt[s.charAt(+i+%2B+2)];
++++++++++++buffer[index%2B%2B]=+(byte)(((c1+<<+4)+%7C+(c2+>>+2))+&+mask);
++++++++++++if(index+>=+buffer.length){
++++++++++++++++return+buffer;
++++++++++++}
++++++++++++int+c3+=+toInt[s.charAt(+i+%2B+3+)];
++++++++++++buffer[index%2B%2B]=+(byte)(((c2+<<+6)+%7C+c3)+&+mask);
++++++++}
++++++++return+buffer;
++++}+

}|code-block|syntax|javascript|1429420|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

My solution is fastest and easiest.

<pre><code>public class MyBase64 {

 private final static char[] ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".toCharArray();

 private static int[] toInt = new int[128];

 static {
 for(int i=0; i&lt; ALPHABET.length; i++){
 toInt[ALPHABET[i]]= i;
 }
 }

 /**
 * Translates the specified byte array into Base64 string.
 *
 * @param buf the byte array (not null)
 * @return the translated Base64 string (not null)
 */
 public static String encode(byte[] buf){
 int size = buf.length;
 char[] ar = new char[((size + 2) / 3) * 4];
 int a = 0;
 int i=0;
 while(i &lt; size){
 byte b0 = buf[i++];
 byte b1 = (i &lt; size) ? buf[i++] : 0;
 byte b2 = (i &lt; size) ? buf[i++] : 0;

 int mask = 0x3F;
 ar[a++] = ALPHABET[(b0 &gt;&gt; 2) &amp; mask];
 ar[a++] = ALPHABET[((b0 &lt;&lt; 4) | ((b1 &amp; 0xFF) &gt;&gt; 4)) &amp; mask];
 ar[a++] = ALPHABET[((b1 &lt;&lt; 2) | ((b2 &amp; 0xFF) &gt;&gt; 6)) &amp; mask];
 ar[a++] = ALPHABET[b2 &amp; mask];
 }
 switch(size % 3){
 case 1: ar[--a] = '=';
 case 2: ar[--a] = '=';
 }
 return new String(ar);
 }

 /**
 * Translates the specified Base64 string into a byte array.
 *
 * @param s the Base64 string (not null)
 * @return the byte array (not null)
 */
 public static byte[] decode(String s){
 int delta = s.endsWith( "==" ) ? 2 : s.endsWith( "=" ) ? 1 : 0;
 byte[] buffer = new byte[s.length()*3/4 - delta];
 int mask = 0xFF;
 int index = 0;
 for(int i=0; i&lt; s.length(); i+=4){
 int c0 = toInt[s.charAt( i )];
 int c1 = toInt[s.charAt( i + 1)];
 buffer[index++]= (byte)(((c0 &lt;&lt; 2) | (c1 &gt;&gt; 4)) &amp; mask);
 if(index &gt;= buffer.length){
 return buffer;
 }
 int c2 = toInt[s.charAt( i + 2)];
 buffer[index++]= (byte)(((c1 &lt;&lt; 4) | (c2 &gt;&gt; 2)) &amp; mask);
 if(index &gt;= buffer.length){
 return buffer;
 }
 int c3 = toInt[s.charAt( i + 3 )];
 buffer[index++]= (byte)(((c2 &lt;&lt; 6) | c3) &amp; mask);
 }
 return buffer;
 } 

}
</code></pre>

blocks|key|1644367|text|希望这能对你有所帮助：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1644368|import+com.sun.org.apache.xml.internal.security.utils.Base64;
String+str="Hello+World";
String+base64_str=Base64.encode(str.getBytes("UTF-8"));|code-block|syntax|javascript|1644369|或者：|1644370|String+str="Hello+World";
String+base64_str="";
try
+++{base64_str=(String)Class.forName("java.util.prefs.Base64").getDeclaredMethod("byteArrayToBase64",+new+Class[]{byte[].class}).invoke(null,+new+Object[]{str.getBytes("UTF-8")});
+++}
catch+(Exception+ee)+{}|1644371|java.util.prefs.Base64在本地rt.jar上工作，|offset|length|style|CODE|1644372|但它不在The+JRE+Class+White+List中|1644373|而不是在Available+classes+not+listed+in+the+GAE/J+white-list中|1644374|太遗憾了!|1644375|PS。在android中，这很容易，因为android.util.Base64是从Android+API+Level+8开始就包含的。|1644376|entityMap|0|LINK|mutability|MUTABLE|url|http://code.google.com/appengine/docs/java/jrewhitelist.html|1|http://blog.stringbuffer.com/2009/04/available-classes-in-google-app-enginej.html^0|0|0|0|0|0|M|P|6|0|4|O|0|0|4|1G|1|0|0|K|J|0^^$0|@$1|2|3|4|5|6|7|18|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|19|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|1A|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|1B|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|1C|8|@$M|1D|N|1E|O|P]|$M|1F|N|1G|O|P]]|9|@]|A|$]]|$1|Q|3|R|5|6|7|1H|8|@]|9|@$M|1I|N|1J|1|1K]]|A|$]]|$1|S|3|T|5|6|7|1L|8|@]|9|@$M|1M|N|1N|1|1O]]|A|$]]|$1|U|3|V|5|6|7|1P|8|@]|9|@]|A|$]]|$1|W|3|X|5|6|7|1Q|8|@$M|1R|N|1S|O|P]]|9|@]|A|$]]|$1|Y|3|-4|5|6|7|1T|8|@]|9|@]|A|$]]]|Z|$10|$5|11|12|13|A|$14|15]]|16|$5|11|12|13|A|$14|17]]]]

Hope this helps you: 

<pre><code>import com.sun.org.apache.xml.internal.security.utils.Base64;
String str="Hello World";
String base64_str=Base64.encode(str.getBytes("UTF-8"));
</code></pre>

Or:

<pre><code>String str="Hello World";
String base64_str="";
try
 {base64_str=(String)Class.forName("java.util.prefs.Base64").getDeclaredMethod("byteArrayToBase64", new Class[]{byte[].class}).invoke(null, new Object[]{str.getBytes("UTF-8")});
 }
catch (Exception ee) {}
</code></pre>

<code>java.util.prefs.Base64</code> works on local <code>rt.jar</code>,

But it is not in <a href="http://code.google.com/appengine/docs/java/jrewhitelist.html" rel="nofollow">The JRE Class White List</a>

and not in <a href="http://blog.stringbuffer.com/2009/04/available-classes-in-google-app-enginej.html" rel="nofollow">Available classes not listed in the GAE/J white-list</a>

What a pity!

PS. In android, it's easy because that <code>android.util.Base64</code> has been included since Android API Level 8.

blocks|key|1429498|text|如果你更喜欢基于性能的解决方案，那么你可以使用"MiGBase64“|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1429499|http://migbase64.sourceforge.net/|offset|length|1429500|public+class+Base64Test+{
++++public+static+void+main(String[]+args)+{
++++String+encodeToString+=+Base64.encodeToString("JavaTips.net".getBytes(),+true);
++++System.out.println("encodeToString+"+%2B+encodeToString);
++++byte[]+decodedBytes+=+Base64.decode(encodeToString.getBytes());
++++System.out.println("decodedBytes+"+%2B+new+String(decodedBytes));
++++}
}|code-block|syntax|javascript|1429501|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|X|0|0|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|S|8|@]|9|@$D|T|E|U|1|V]]|A|$]]|$1|F|3|G|5|H|7|W|8|@]|9|@]|A|$I|J]]|$1|K|3|-4|5|6|7|X|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|C]]]]

If You are prefering performance based solution then you can use "MiGBase64"

<a href="http://migbase64.sourceforge.net/" rel="noreferrer">http://migbase64.sourceforge.net/</a>

<pre><code>public class Base64Test {
 public static void main(String[] args) {
 String encodeToString = Base64.encodeToString("JavaTips.net".getBytes(), true);
 System.out.println("encodeToString " + encodeToString);
 byte[] decodedBytes = Base64.decode(encodeToString.getBytes());
 System.out.println("decodedBytes " + new String(decodedBytes));
 }
}
</code></pre>

blocks|key|1429539|text|另一个迟来的答案，但我的基准测试表明Jetty's+implementation+of+Base64编码器相当快。它的速度没有MiGBase64快，但比iHarder+Base64快。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1429540|import+org.eclipse.jetty.util.B64Code;

final+String+decoded+=+B64Code.decode(encoded,+"UTF-8");|code-block|syntax|javascript|1429541|我还做了一些基准测试：|1429542|++++++library+++++%7C++++encode++++%7C++++decode+++
------------------%2B--------------%2B-------------
+'MiGBase64'++++++%7C++10146001.00+%7C++6426446.00
+'Jetty+B64Code'++%7C+++8846191.00+%7C++3101361.75
+'iHarder+Base64'+%7C+++3259590.50+%7C++2505280.00
+'Commons-Codec'++%7C++++241318.04+%7C+++255179.96|1429543|这些是运行/秒，所以越高越好。|1429544|entityMap|0|LINK|mutability|MUTABLE|url|http://download.eclipse.org/jetty/stable-7/apidocs/org/eclipse/jetty/util/B64Code.html|1|http://migbase64.sourceforge.net/|2|http://iharder.sourceforge.net/current/java/base64/^0|I|W|0|1R|9|1|24|E|2|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@$A|11|B|12|1|13]|$A|14|B|15|1|16]|$A|17|B|18|1|19]]|C|$]]|$1|D|3|E|5|F|7|1A|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|1B|8|@]|9|@]|C|$]]|$1|K|3|L|5|F|7|1C|8|@]|9|@]|C|$G|H]]|$1|M|3|N|5|6|7|1D|8|@]|9|@]|C|$]]|$1|O|3|-4|5|6|7|1E|8|@]|9|@]|C|$]]]|P|$Q|$5|R|S|T|C|$U|V]]|W|$5|R|S|T|C|$U|X]]|Y|$5|R|S|T|C|$U|Z]]]]

Another late answer, but my benchmarking shows that <a href="http://download.eclipse.org/jetty/stable-7/apidocs/org/eclipse/jetty/util/B64Code.html" rel="noreferrer">Jetty's implementation of Base64</a> encoder is pretty fast. Not as fast as <a href="http://migbase64.sourceforge.net/" rel="noreferrer">MiGBase64</a> but faster than <a href="http://iharder.sourceforge.net/current/java/base64/" rel="noreferrer">iHarder Base64</a>.

<pre><code>import org.eclipse.jetty.util.B64Code;

final String decoded = B64Code.decode(encoded, "UTF-8");
</code></pre>

I also did some benchmarks:

<pre><code> library | encode | decode 
------------------+--------------+-------------
 'MiGBase64' | 10146001.00 | 6426446.00
 'Jetty B64Code' | 8846191.00 | 3101361.75
 'iHarder Base64' | 3259590.50 | 2505280.00
 'Commons-Codec' | 241318.04 | 255179.96
</code></pre>

These are runs/sec so higher is better.

blocks|key|1644453|text|下面是我自己的实现，如果对某些人有用的话：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1644454|public+class+Base64Coder+{

++++//+The+line+separator+string+of+the+operating+system.
++++private+static+final+String+systemLineSeparator+=+System.getProperty("line.separator");

++++//+Mapping+table+from+6-bit+nibbles+to+Base64+characters.
++++private+static+final+char[]+map1+=+new+char[64];
+++++++static+{
++++++++++int+i=0;
++++++++++for+(char+c='A';+c<='Z';+c%2B%2B)+map1[i%2B%2B]+=+c;
++++++++++for+(char+c='a';+c<='z';+c%2B%2B)+map1[i%2B%2B]+=+c;
++++++++++for+(char+c='0';+c<='9';+c%2B%2B)+map1[i%2B%2B]+=+c;
++++++++++map1[i%2B%2B]+=+'%2B';+map1[i%2B%2B]+=+'/';+}

++++//+Mapping+table+from+Base64+characters+to+6-bit+nibbles.
++++private+static+final+byte[]+map2+=+new+byte[128];
+++++++static+{
++++++++++for+(int+i=0;+i<map2.length;+i%2B%2B)+map2[i]+=+-1;
++++++++++for+(int+i=0;+i<64;+i%2B%2B)+map2[map1[i]]+=+(byte)i;+}

++++/**
++++*+Encodes+a+string+into+Base64+format.
++++*+No+blanks+or+line+breaks+are+inserted.
++++*+@param+s++A+String+to+be+encoded.
++++*+@return+++A+String+containing+the+Base64+encoded+data.
++++*/
++++public+static+String+encodeString+(String+s)+{
+++++++return+new+String(encode(s.getBytes()));+}

++++/**
++++*+Encodes+a+byte+array+into+Base+64+format+and+breaks+the+output+into+lines+of+76+characters.
++++*+This+method+is+compatible+with+<code>sun.misc.BASE64Encoder.encodeBuffer(byte[])</code>.
++++*+@param+in++An+array+containing+the+data+bytes+to+be+encoded.
++++*+@return++++A+String+containing+the+Base64+encoded+data,+broken+into+lines.
++++*/
++++public+static+String+encodeLines+(byte[]+in)+{
+++++++return+encodeLines(in,+0,+in.length,+76,+systemLineSeparator);+}

++++/**
++++*+Encodes+a+byte+array+into+Base+64+format+and+breaks+the+output+into+lines.
++++*+@param+in++++++++++++An+array+containing+the+data+bytes+to+be+encoded.
++++*+@param+iOff++++++++++Offset+of+the+first+byte+in+<code>in</code>+to+be+processed.
++++*+@param+iLen++++++++++Number+of+bytes+to+be+processed+in+<code>in</code>,+starting+at+<code>iOff</code>.
++++*+@param+lineLen+++++++Line+length+for+the+output+data.+Should+be+a+multiple+of+4.
++++*+@param+lineSeparator+The+line+separator+to+be+used+to+separate+the+output+lines.
++++*+@return++++++++++++++A+String+containing+the+Base64+encoded+data,+broken+into+lines.
++++*/
++++public+static+String+encodeLines+(byte[]+in,+int+iOff,+int+iLen,+int+lineLen,+String+lineSeparator)+{
+++++++int+blockLen+=+(lineLen*3)+/+4;
+++++++if+(blockLen+<=+0)+throw+new+IllegalArgumentException();
+++++++int+lines+=+(iLen%2BblockLen-1)+/+blockLen;
+++++++int+bufLen+=+((iLen%2B2)/3)*4+%2B+lines*lineSeparator.length();
+++++++StringBuilder+buf+=+new+StringBuilder(bufLen);
+++++++int+ip+=+0;
+++++++while+(ip+<+iLen)+{
++++++++++int+l+=+Math.min(iLen-ip,+blockLen);
++++++++++buf.append+(encode(in,+iOff%2Bip,+l));
++++++++++buf.append+(lineSeparator);
++++++++++ip+%2B=+l;+}
+++++++return+buf.toString();+}

++++/**
++++*+Encodes+a+byte+array+into+Base64+format.
++++*+No+blanks+or+line+breaks+are+inserted+in+the+output.
++++*+@param+in++An+array+containing+the+data+bytes+to+be+encoded.
++++*+@return++++A+character+array+containing+the+Base64+encoded+data.
++++*/
++++public+static+char[]+encode+(byte[]+in)+{
+++++++return+encode(in,+0,+in.length);+}

++++/**
++++*+Encodes+a+byte+array+into+Base64+format.
++++*+No+blanks+or+line+breaks+are+inserted+in+the+output.
++++*+@param+in++++An+array+containing+the+data+bytes+to+be+encoded.
++++*+@param+iLen++Number+of+bytes+to+process+in+<code>in</code>.
++++*+@return++++++A+character+array+containing+the+Base64+encoded+data.
++++*/
++++public+static+char[]+encode+(byte[]+in,+int+iLen)+{
+++++++return+encode(in,+0,+iLen);+}

++++/**
++++*+Encodes+a+byte+array+into+Base64+format.
++++*+No+blanks+or+line+breaks+are+inserted+in+the+output.
++++*+@param+in++++An+array+containing+the+data+bytes+to+be+encoded.
++++*+@param+iOff++Offset+of+the+first+byte+in+<code>in</code>+to+be+processed.
++++*+@param+iLen++Number+of+bytes+to+process+in+<code>in</code>,+starting+at+<code>iOff</code>.
++++*+@return++++++A+character+array+containing+the+Base64+encoded+data.
++++*/
++++public+static+char[]+encode+(byte[]+in,+int+iOff,+int+iLen)+{
+++++++int+oDataLen+=+(iLen*4%2B2)/3;+++++++//+output+length+without+padding
+++++++int+oLen+=+((iLen%2B2)/3)*4;+++++++++//+output+length+including+padding
+++++++char[]+out+=+new+char[oLen];
+++++++int+ip+=+iOff;
+++++++int+iEnd+=+iOff+%2B+iLen;
+++++++int+op+=+0;
+++++++while+(ip+<+iEnd)+{
++++++++++int+i0+=+in[ip%2B%2B]+&+0xff;
++++++++++int+i1+=+ip+<+iEnd+?+in[ip%2B%2B]+&+0xff+:+0;
++++++++++int+i2+=+ip+<+iEnd+?+in[ip%2B%2B]+&+0xff+:+0;
++++++++++int+o0+=+i0+>>>+2;
++++++++++int+o1+=+((i0+&+++3)+<<+4)+%7C+(i1+>>>+4);
++++++++++int+o2+=+((i1+&+0xf)+<<+2)+%7C+(i2+>>>+6);
++++++++++int+o3+=+i2+&+0x3F;
++++++++++out[op%2B%2B]+=+map1[o0];
++++++++++out[op%2B%2B]+=+map1[o1];
++++++++++out[op]+=+op+<+oDataLen+?+map1[o2]+:+'=';+op%2B%2B;
++++++++++out[op]+=+op+<+oDataLen+?+map1[o3]+:+'=';+op%2B%2B;+}
+++++++return+out;+}

++++/**
++++*+Decodes+a+string+from+Base64+format.
++++*+No+blanks+or+line+breaks+are+allowed+within+the+Base64+encoded+input+data.
++++*+@param+s++A+Base64+String+to+be+decoded.
++++*+@return+++A+String+containing+the+decoded+data.
++++*+@throws+++IllegalArgumentException+If+the+input+is+not+valid+Base64+encoded+data.
++++*/
++++public+static+String+decodeString+(String+s)+{
+++++++return+new+String(decode(s));+}

++++/**
++++*+Decodes+a+byte+array+from+Base64+format+and+ignores+line+separators,+tabs+and+blanks.
++++*+CR,+LF,+Tab+and+Space+characters+are+ignored+in+the+input+data.
++++*+This+method+is+compatible+with+<code>sun.misc.BASE64Decoder.decodeBuffer(String)</code>.
++++*+@param+s++A+Base64+String+to+be+decoded.
++++*+@return+++An+array+containing+the+decoded+data+bytes.
++++*+@throws+++IllegalArgumentException+If+the+input+is+not+valid+Base64+encoded+data.
++++*/
++++public+static+byte[]+decodeLines+(String+s)+{
+++++++char[]+buf+=+new+char[s.length()];
+++++++int+p+=+0;
+++++++for+(int+ip+=+0;+ip+<+s.length();+ip%2B%2B)+{
++++++++++char+c+=+s.charAt(ip);
++++++++++if+(c+!=+'+'+&&+c+!=+'\r'+&&+c+!=+'\n'+&&+c+!=+'\t')
+++++++++++++buf[p%2B%2B]+=+c;+}
+++++++return+decode(buf,+0,+p);+}

++++/**
++++*+Decodes+a+byte+array+from+Base64+format.
++++*+No+blanks+or+line+breaks+are+allowed+within+the+Base64+encoded+input+data.
++++*+@param+s++A+Base64+String+to+be+decoded.
++++*+@return+++An+array+containing+the+decoded+data+bytes.
++++*+@throws+++IllegalArgumentException+If+the+input+is+not+valid+Base64+encoded+data.
++++*/
++++public+static+byte[]+decode+(String+s)+{
+++++++return+decode(s.toCharArray());+}

++++/**
++++*+Decodes+a+byte+array+from+Base64+format.
++++*+No+blanks+or+line+breaks+are+allowed+within+the+Base64+encoded+input+data.
++++*+@param+in++A+character+array+containing+the+Base64+encoded+data.
++++*+@return++++An+array+containing+the+decoded+data+bytes.
++++*+@throws++++IllegalArgumentException+If+the+input+is+not+valid+Base64+encoded+data.
++++*/
++++public+static+byte[]+decode+(char[]+in)+{
+++++++return+decode(in,+0,+in.length);+}

++++/**
++++*+Decodes+a+byte+array+from+Base64+format.
++++*+No+blanks+or+line+breaks+are+allowed+within+the+Base64+encoded+input+data.
++++*+@param+in++++A+character+array+containing+the+Base64+encoded+data.
++++*+@param+iOff++Offset+of+the+first+character+in+<code>in</code>+to+be+processed.
++++*+@param+iLen++Number+of+characters+to+process+in+<code>in</code>,+starting+at+<code>iOff</code>.
++++*+@return++++++An+array+containing+the+decoded+data+bytes.
++++*+@throws++++++IllegalArgumentException+If+the+input+is+not+valid+Base64+encoded+data.
++++*/
++++public+static+byte[]+decode+(char[]+in,+int+iOff,+int+iLen)+{
+++++++if+(iLen%254+!=+0)+throw+new+IllegalArgumentException+("Length+of+Base64+encoded+input+string+is+not+a+multiple+of+4.");
+++++++while+(iLen+>+0+&&+in[iOff%2BiLen-1]+==+'=')+iLen--;
+++++++int+oLen+=+(iLen*3)+/+4;
+++++++byte[]+out+=+new+byte[oLen];
+++++++int+ip+=+iOff;
+++++++int+iEnd+=+iOff+%2B+iLen;
+++++++int+op+=+0;
+++++++while+(ip+<+iEnd)+{
++++++++++int+i0+=+in[ip%2B%2B];
++++++++++int+i1+=+in[ip%2B%2B];
++++++++++int+i2+=+ip+<+iEnd+?+in[ip%2B%2B]+:+'A';
++++++++++int+i3+=+ip+<+iEnd+?+in[ip%2B%2B]+:+'A';
++++++++++if+(i0+>+127+%7C%7C+i1+>+127+%7C%7C+i2+>+127+%7C%7C+i3+>+127)
+++++++++++++throw+new+IllegalArgumentException+("Illegal+character+in+Base64+encoded+data.");
++++++++++int+b0+=+map2[i0];
++++++++++int+b1+=+map2[i1];
++++++++++int+b2+=+map2[i2];
++++++++++int+b3+=+map2[i3];
++++++++++if+(b0+<+0+%7C%7C+b1+<+0+%7C%7C+b2+<+0+%7C%7C+b3+<+0)
+++++++++++++throw+new+IllegalArgumentException+("Illegal+character+in+Base64+encoded+data.");
++++++++++int+o0+=+(+b0+++++++<<2)+%7C+(b1>>>4);
++++++++++int+o1+=+((b1+&+0xf)<<4)+%7C+(b2>>>2);
++++++++++int+o2+=+((b2+&+++3)<<6)+%7C++b3;
++++++++++out[op%2B%2B]+=+(byte)o0;
++++++++++if+(op<oLen)+out[op%2B%2B]+=+(byte)o1;
++++++++++if+(op<oLen)+out[op%2B%2B]+=+(byte)o2;+}
+++++++return+out;+}

++++//+Dummy+constructor.
++++private+Base64Coder()+{}
}|code-block|syntax|javascript|1644455|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Here's my own implementation, if it could be useful to someone : 

<pre><code>public class Base64Coder {

 // The line separator string of the operating system.
 private static final String systemLineSeparator = System.getProperty("line.separator");

 // Mapping table from 6-bit nibbles to Base64 characters.
 private static final char[] map1 = new char[64];
 static {
 int i=0;
 for (char c='A'; c&lt;='Z'; c++) map1[i++] = c;
 for (char c='a'; c&lt;='z'; c++) map1[i++] = c;
 for (char c='0'; c&lt;='9'; c++) map1[i++] = c;
 map1[i++] = '+'; map1[i++] = '/'; }

 // Mapping table from Base64 characters to 6-bit nibbles.
 private static final byte[] map2 = new byte[128];
 static {
 for (int i=0; i&lt;map2.length; i++) map2[i] = -1;
 for (int i=0; i&lt;64; i++) map2[map1[i]] = (byte)i; }

 /**
 * Encodes a string into Base64 format.
 * No blanks or line breaks are inserted.
 * @param s A String to be encoded.
 * @return A String containing the Base64 encoded data.
 */
 public static String encodeString (String s) {
 return new String(encode(s.getBytes())); }

 /**
 * Encodes a byte array into Base 64 format and breaks the output into lines of 76 characters.
 * This method is compatible with &lt;code&gt;sun.misc.BASE64Encoder.encodeBuffer(byte[])&lt;/code&gt;.
 * @param in An array containing the data bytes to be encoded.
 * @return A String containing the Base64 encoded data, broken into lines.
 */
 public static String encodeLines (byte[] in) {
 return encodeLines(in, 0, in.length, 76, systemLineSeparator); }

 /**
 * Encodes a byte array into Base 64 format and breaks the output into lines.
 * @param in An array containing the data bytes to be encoded.
 * @param iOff Offset of the first byte in &lt;code&gt;in&lt;/code&gt; to be processed.
 * @param iLen Number of bytes to be processed in &lt;code&gt;in&lt;/code&gt;, starting at &lt;code&gt;iOff&lt;/code&gt;.
 * @param lineLen Line length for the output data. Should be a multiple of 4.
 * @param lineSeparator The line separator to be used to separate the output lines.
 * @return A String containing the Base64 encoded data, broken into lines.
 */
 public static String encodeLines (byte[] in, int iOff, int iLen, int lineLen, String lineSeparator) {
 int blockLen = (lineLen*3) / 4;
 if (blockLen &lt;= 0) throw new IllegalArgumentException();
 int lines = (iLen+blockLen-1) / blockLen;
 int bufLen = ((iLen+2)/3)*4 + lines*lineSeparator.length();
 StringBuilder buf = new StringBuilder(bufLen);
 int ip = 0;
 while (ip &lt; iLen) {
 int l = Math.min(iLen-ip, blockLen);
 buf.append (encode(in, iOff+ip, l));
 buf.append (lineSeparator);
 ip += l; }
 return buf.toString(); }

 /**
 * Encodes a byte array into Base64 format.
 * No blanks or line breaks are inserted in the output.
 * @param in An array containing the data bytes to be encoded.
 * @return A character array containing the Base64 encoded data.
 */
 public static char[] encode (byte[] in) {
 return encode(in, 0, in.length); }

 /**
 * Encodes a byte array into Base64 format.
 * No blanks or line breaks are inserted in the output.
 * @param in An array containing the data bytes to be encoded.
 * @param iLen Number of bytes to process in &lt;code&gt;in&lt;/code&gt;.
 * @return A character array containing the Base64 encoded data.
 */
 public static char[] encode (byte[] in, int iLen) {
 return encode(in, 0, iLen); }

 /**
 * Encodes a byte array into Base64 format.
 * No blanks or line breaks are inserted in the output.
 * @param in An array containing the data bytes to be encoded.
 * @param iOff Offset of the first byte in &lt;code&gt;in&lt;/code&gt; to be processed.
 * @param iLen Number of bytes to process in &lt;code&gt;in&lt;/code&gt;, starting at &lt;code&gt;iOff&lt;/code&gt;.
 * @return A character array containing the Base64 encoded data.
 */
 public static char[] encode (byte[] in, int iOff, int iLen) {
 int oDataLen = (iLen*4+2)/3; // output length without padding
 int oLen = ((iLen+2)/3)*4; // output length including padding
 char[] out = new char[oLen];
 int ip = iOff;
 int iEnd = iOff + iLen;
 int op = 0;
 while (ip &lt; iEnd) {
 int i0 = in[ip++] &amp; 0xff;
 int i1 = ip &lt; iEnd ? in[ip++] &amp; 0xff : 0;
 int i2 = ip &lt; iEnd ? in[ip++] &amp; 0xff : 0;
 int o0 = i0 &gt;&gt;&gt; 2;
 int o1 = ((i0 &amp; 3) &lt;&lt; 4) | (i1 &gt;&gt;&gt; 4);
 int o2 = ((i1 &amp; 0xf) &lt;&lt; 2) | (i2 &gt;&gt;&gt; 6);
 int o3 = i2 &amp; 0x3F;
 out[op++] = map1[o0];
 out[op++] = map1[o1];
 out[op] = op &lt; oDataLen ? map1[o2] : '='; op++;
 out[op] = op &lt; oDataLen ? map1[o3] : '='; op++; }
 return out; }

 /**
 * Decodes a string from Base64 format.
 * No blanks or line breaks are allowed within the Base64 encoded input data.
 * @param s A Base64 String to be decoded.
 * @return A String containing the decoded data.
 * @throws IllegalArgumentException If the input is not valid Base64 encoded data.
 */
 public static String decodeString (String s) {
 return new String(decode(s)); }

 /**
 * Decodes a byte array from Base64 format and ignores line separators, tabs and blanks.
 * CR, LF, Tab and Space characters are ignored in the input data.
 * This method is compatible with &lt;code&gt;sun.misc.BASE64Decoder.decodeBuffer(String)&lt;/code&gt;.
 * @param s A Base64 String to be decoded.
 * @return An array containing the decoded data bytes.
 * @throws IllegalArgumentException If the input is not valid Base64 encoded data.
 */
 public static byte[] decodeLines (String s) {
 char[] buf = new char[s.length()];
 int p = 0;
 for (int ip = 0; ip &lt; s.length(); ip++) {
 char c = s.charAt(ip);
 if (c != ' ' &amp;&amp; c != '\r' &amp;&amp; c != '\n' &amp;&amp; c != '\t')
 buf[p++] = c; }
 return decode(buf, 0, p); }

 /**
 * Decodes a byte array from Base64 format.
 * No blanks or line breaks are allowed within the Base64 encoded input data.
 * @param s A Base64 String to be decoded.
 * @return An array containing the decoded data bytes.
 * @throws IllegalArgumentException If the input is not valid Base64 encoded data.
 */
 public static byte[] decode (String s) {
 return decode(s.toCharArray()); }

 /**
 * Decodes a byte array from Base64 format.
 * No blanks or line breaks are allowed within the Base64 encoded input data.
 * @param in A character array containing the Base64 encoded data.
 * @return An array containing the decoded data bytes.
 * @throws IllegalArgumentException If the input is not valid Base64 encoded data.
 */
 public static byte[] decode (char[] in) {
 return decode(in, 0, in.length); }

 /**
 * Decodes a byte array from Base64 format.
 * No blanks or line breaks are allowed within the Base64 encoded input data.
 * @param in A character array containing the Base64 encoded data.
 * @param iOff Offset of the first character in &lt;code&gt;in&lt;/code&gt; to be processed.
 * @param iLen Number of characters to process in &lt;code&gt;in&lt;/code&gt;, starting at &lt;code&gt;iOff&lt;/code&gt;.
 * @return An array containing the decoded data bytes.
 * @throws IllegalArgumentException If the input is not valid Base64 encoded data.
 */
 public static byte[] decode (char[] in, int iOff, int iLen) {
 if (iLen%4 != 0) throw new IllegalArgumentException ("Length of Base64 encoded input string is not a multiple of 4.");
 while (iLen &gt; 0 &amp;&amp; in[iOff+iLen-1] == '=') iLen--;
 int oLen = (iLen*3) / 4;
 byte[] out = new byte[oLen];
 int ip = iOff;
 int iEnd = iOff + iLen;
 int op = 0;
 while (ip &lt; iEnd) {
 int i0 = in[ip++];
 int i1 = in[ip++];
 int i2 = ip &lt; iEnd ? in[ip++] : 'A';
 int i3 = ip &lt; iEnd ? in[ip++] : 'A';
 if (i0 &gt; 127 || i1 &gt; 127 || i2 &gt; 127 || i3 &gt; 127)
 throw new IllegalArgumentException ("Illegal character in Base64 encoded data.");
 int b0 = map2[i0];
 int b1 = map2[i1];
 int b2 = map2[i2];
 int b3 = map2[i3];
 if (b0 &lt; 0 || b1 &lt; 0 || b2 &lt; 0 || b3 &lt; 0)
 throw new IllegalArgumentException ("Illegal character in Base64 encoded data.");
 int o0 = ( b0 &lt;&lt;2) | (b1&gt;&gt;&gt;4);
 int o1 = ((b1 &amp; 0xf)&lt;&lt;4) | (b2&gt;&gt;&gt;2);
 int o2 = ((b2 &amp; 3)&lt;&lt;6) | b3;
 out[op++] = (byte)o0;
 if (op&lt;oLen) out[op++] = (byte)o1;
 if (op&lt;oLen) out[op++] = (byte)o2; }
 return out; }

 // Dummy constructor.
 private Base64Coder() {}
}
</code></pre>

blocks|key|1429679|text|Guava现在内置了Base64解码功能。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1429680|使用BaseEncoding.base64().decode()|offset|length|1429681|至于如何处理输入使用中可能出现的空格|1429682|BaseEncoding.base64().decode(CharMatcher.WHITESPACE.removeFrom(...));|style|CODE|1429683|有关更多信息，请参阅this+discussion|1429684|entityMap|0|LINK|mutability|MUTABLE|url|http://google.github.io/guava/releases/snapshot-jre/api/docs/com/google/common/io/BaseEncoding.html|1|https://github.com/google/guava/issues/1252^0|0|2|U|0|0|0|0|1X|0|A|F|1|0^^$0|@$1|2|3|4|5|6|7|X|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Y|8|@]|9|@$D|Z|E|10|1|11]]|A|$]]|$1|F|3|G|5|6|7|12|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|13|8|@$D|14|E|15|J|K]]|9|@]|A|$]]|$1|L|3|M|5|6|7|16|8|@]|9|@$D|17|E|18|1|19]]|A|$]]|$1|N|3|-4|5|6|7|1A|8|@]|9|@]|A|$]]]|O|$P|$5|Q|R|S|A|$T|U]]|V|$5|Q|R|S|A|$T|W]]]]

Guava now has Base64 decoding built in. 

Use <a href="http://google.github.io/guava/releases/snapshot-jre/api/docs/com/google/common/io/BaseEncoding.html" rel="nofollow noreferrer">BaseEncoding.base64().decode()</a> 

As for dealing with possible whitespace in input use

<code>BaseEncoding.base64().decode(CharMatcher.WHITESPACE.removeFrom(...));</code>

See <a href="https://github.com/google/guava/issues/1252" rel="nofollow noreferrer">this discussion</a> for more information

blocks|key|1429748|text|您可以从编码的Base64字符串中写入或下载文件：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1429749|Base64+base64+=+new+Base64();+
String+encodedFile="JVBERi0xLjUKJeLjz9MKMSAwIG9iago8PCAKICAgL1R5cGUgL0NhdGFsb2cKICAgL1BhZ2VzIDIgMCBSCiAgIC9QYWdlTGF5b3V0IC9TaW5";+
++++++++++++++byte[]+dd=encodedFile.getBytes();
++++++++++++byte[]+bytes+=+Base64.decodeBase64(dd);

+response.setHeader("Content-disposition",+"attachment;+filename=\""%2Bfilename%2B"\"");
++++++++++++response.setHeader("Cache-Control",+"no-cache");
++++++++++++response.setHeader("Expires",+"-1");

++++++++++++//+actually+send+result+bytes
++++++++++++response.getOutputStream().write(bytes);|code-block|syntax|javascript|1429750|为我工作，希望也为你工作...|1429751|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

You can write or download file from encoded Base64 string:

<pre><code>Base64 base64 = new Base64(); 
String encodedFile="JVBERi0xLjUKJeLjz9MKMSAwIG9iago8PCAKICAgL1R5cGUgL0NhdGFsb2cKICAgL1BhZ2VzIDIgMCBSCiAgIC9QYWdlTGF5b3V0IC9TaW5"; 
 byte[] dd=encodedFile.getBytes();
 byte[] bytes = Base64.decodeBase64(dd);

 response.setHeader("Content-disposition", "attachment; filename=\""+filename+"\"");
 response.setHeader("Cache-Control", "no-cache");
 response.setHeader("Expires", "-1");

 // actually send result bytes
 response.getOutputStream().write(bytes);
</code></pre>

Worked for me and hopefully for you also...

blocks|key|1644708|text|java.util.Base64的Java8实现不依赖于其他Java8特定的类。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1644709|我不确定这是否适用于Java6项目，但是可以将Base64.java文件复制并粘贴到Java7项目中，并且除了导入java.util.Arrays和java.util.Objects之外，不需要任何修改就可以编译它。|1644710|注意Base64.java文件包含在GNU+GPL2中|1644711|entityMap^0|0|G|0|N|B|22|H|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@$9|M|A|N|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|O|8|@$9|P|A|Q|B|C]|$9|R|A|S|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|T|8|@]|D|@]|E|$]]|$1|J|3|-4|5|6|7|U|8|@]|D|@]|E|$]]]|K|$]]

The Java 8 implementation of <code>java.util.Base64</code> has no dependencies on other Java 8 specific classes.

I am not certain if this will work for Java 6 project, but it is possible to copy and paste the <code>Base64.java</code> file into a Java 7 project and compile it with no modification other than importing java.util.Arrays and <code>java.util.Objects</code>.

Note the Base64.java file is covered by the GNU GPL2

blocks|key|1644766|text|在用Java7编译但可能运行在更高Java版本中的代码中，检测java.util.Base64类的存在似乎很有用，并使用此处其他问题中提到的最适合给定JVM的方法。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1644767|我使用了以下代码：|1644768|private+static+final+Method+JAVA_UTIL_BASE64_GETENCODER;

static+{
++++Method+getEncoderMethod;
++++try+{
++++++++final+Class<?>+base64Class+=+Class.forName("java.util.Base64");
++++++++getEncoderMethod+=+base64Class.getMethod("getEncoder");
++++}+catch+(ClassNotFoundException+%7C+NoSuchMethodException+e)+{
++++++++getEncoderMethod+=+null;
++++}
++++JAVA_UTIL_BASE64_GETENCODER+=+getEncoderMethod;
}

static+String+base64EncodeToString(String+s)+{
++++final+byte[]+bytes+=+s.getBytes(StandardCharsets.ISO_8859_1);
++++if+(JAVA_UTIL_BASE64_GETENCODER+==+null)+{
++++++++//+Java+7+and+older+//+TODO:+remove+this+branch+after+switching+to+Java+8
++++++++return+DatatypeConverter.printBase64Binary(bytes);
++++}+else+{
++++++++//+Java+8+and+newer
++++++++try+{
++++++++++++final+Object+encoder+=+JAVA_UTIL_BASE64_GETENCODER.invoke(null);
++++++++++++final+Class<?>+encoderClass+=+encoder.getClass();
++++++++++++final+Method+encodeMethod+=+encoderClass.getMethod("encode",+byte[].class);
++++++++++++final+byte[]+encodedBytes+=+(byte[])+encodeMethod.invoke(encoder,+bytes);
++++++++++++return+new+String(encodedBytes);
++++++++}+catch+(NoSuchMethodException+%7C+IllegalAccessException+%7C+InvocationTargetException+e)+{
++++++++++++throw+new+IllegalStateException(e);
++++++++}
++++}
}|code-block|syntax|javascript|1644769|entityMap^0|V|G|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|R|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|S|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|N|$]]

In a code compiled with Java 7 but potentially running in a higher java version, it seems useful to detect presence of <code>java.util.Base64</code> class and use the approach best for given JVM mentioned in other questions here.

I used this code:

<pre><code>private static final Method JAVA_UTIL_BASE64_GETENCODER;

static {
 Method getEncoderMethod;
 try {
 final Class&lt;?&gt; base64Class = Class.forName("java.util.Base64");
 getEncoderMethod = base64Class.getMethod("getEncoder");
 } catch (ClassNotFoundException | NoSuchMethodException e) {
 getEncoderMethod = null;
 }
 JAVA_UTIL_BASE64_GETENCODER = getEncoderMethod;
}

static String base64EncodeToString(String s) {
 final byte[] bytes = s.getBytes(StandardCharsets.ISO_8859_1);
 if (JAVA_UTIL_BASE64_GETENCODER == null) {
 // Java 7 and older // TODO: remove this branch after switching to Java 8
 return DatatypeConverter.printBase64Binary(bytes);
 } else {
 // Java 8 and newer
 try {
 final Object encoder = JAVA_UTIL_BASE64_GETENCODER.invoke(null);
 final Class&lt;?&gt; encoderClass = encoder.getClass();
 final Method encodeMethod = encoderClass.getMethod("encode", byte[].class);
 final byte[] encodedBytes = (byte[]) encodeMethod.invoke(encoder, bytes);
 return new String(encodedBytes);
 } catch (NoSuchMethodException | IllegalAccessException | InvocationTargetException e) {
 throw new IllegalStateException(e);
 }
 }
}
</code></pre>

blocks|key|1429882|text|使用Java+8-|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1429883|++++public+static+String+encodeString(String+plainString)+{
++++++++return++Base64.getEncoder().encodeToString(plainString.getBytes());
++++}

++++public+static+String+decodeString(String+encodedString)+{
++++++++byte[]+bytes+=+Base64.getDecoder().decode(encodedString);
++++++++return+new+String(bytes);
++++}|code-block|syntax|javascript|1429884|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Using Java 8 -

<pre><code> public static String encodeString(String plainString) {
 return Base64.getEncoder().encodeToString(plainString.getBytes());
 }

 public static String decodeString(String encodedString) {
 byte[] bytes = Base64.getDecoder().decode(encodedString);
 return new String(bytes);
 }
</code></pre>

blocks|key|1644857|text|你可以简单地试试这个。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1644858|byte[]+data+=+Base64.getDecoder().decode(base64fileContent);|code-block|syntax|javascript|1644859|Base64.getDecode()返回一个可以解码的Base64解码器。然后，您需要使用.decode(<your+base64>)再次解码。|offset|length|style|CODE|1644860|entityMap^0|0|0|0|I|19|M|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]|$I|T|J|U|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|N|$]]

You can simply try this.
<pre><code>byte[] data = Base64.getDecoder().decode(base64fileContent);
</code></pre>
<code>Base64.getDecode()</code> returns a Base64 Decoder that can be decoded. Then you need to decode that again using <code>.decode(&lt;your base64&gt;)</code>.

blocks|key|1644894|text|import+java.io.UnsupportedEncodingException;
import+java.security.MessageDigest;
import+java.security.NoSuchAlgorithmException;
import+java.util.Arrays;
import+java.util.Base64;

import+javax.crypto.Cipher;
import+javax.crypto.spec.SecretKeySpec;
/***
+*+
+*+@author+Vaquar+khan
+*+
+*
+*/
public+class+AES+{

++++private+static+SecretKeySpec+secretKey;
++++private+static+final+String+VK_secretKey+=+"VaquarKhan-secrate-key!!!!";
++++private+static+byte[]+key;

++++/**
+++++*+
+++++*+@param+myKey
+++++*/
++++public+static+void+setKey(String+myKey)+{
++++++++MessageDigest+sha+=+null;
++++++++try+{
++++++++++++key+=+myKey.getBytes("UTF-8");
++++++++++++sha+=+MessageDigest.getInstance("SHA-1");
++++++++++++key+=+sha.digest(key);
++++++++++++key+=+Arrays.copyOf(key,+16);
++++++++++++secretKey+=+new+SecretKeySpec(key,+"AES");
++++++++}+catch+(NoSuchAlgorithmException+e)+{
++++++++++++e.printStackTrace();
++++++++}+catch+(UnsupportedEncodingException+e)+{
++++++++++++e.printStackTrace();
++++++++}
++++}
/**
+*+encrypt
+*+@param+strToEncrypt
+*+@param+secret
+*+@return
+*/
++++public+static+String+encrypt(String+strToEncrypt,+String+secret)+{
++++++++try+{
++++++++++++setKey(secret);
++++++++++++Cipher+cipher+=+Cipher.getInstance("AES/ECB/PKCS5Padding");
++++++++++++cipher.init(Cipher.ENCRYPT_MODE,+secretKey);
++++++++++++return+Base64.getEncoder().encodeToString(cipher.doFinal(strToEncrypt.getBytes("UTF-8")));
++++++++}+catch+(Exception+e)+{
++++++++++++System.out.println("Error+while+encrypting:+"+%2B+e.toString());
++++++++}
++++++++return+null;
++++}
/**
+*+decrypt
+*+@param+strToDecrypt
+*+@param+secret
+*+@return
+*/
++++public+static+String+decrypt(String+strToDecrypt,+String+secret)+{
++++++++try+{
++++++++++++setKey(secret);
++++++++++++Cipher+cipher+=+Cipher.getInstance("AES/ECB/PKCS5PADDING");
++++++++++++cipher.init(Cipher.DECRYPT_MODE,+secretKey);
++++++++++++return+new+String(cipher.doFinal(Base64.getDecoder().decode(strToDecrypt)));
++++++++}+catch+(Exception+e)+{
++++++++++++System.out.println("Error+while+decrypting:+"+%2B+e.toString());
++++++++}
++++++++return+null;
++++}

++++public+static+void+main(String[]+args)+{
++++++++final+String+secretKey+=+VK_secretKey;
++++++++String+password+=+"VKhan@12";
++++++++//
++++++++String+encryptedString+=+AES.encrypt(password,+secretKey);
++++++++String+decryptedString+=+AES.decrypt(encryptedString,+secretKey);
++++++++//
++++++++System.out.println(password);
++++++++System.out.println(encryptedString);
++++++++System.out.println(decryptedString);
++++}

}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1644895|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;
import java.util.Base64;

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
/***
 * 
 * @author Vaquar khan
 * 
 *
 */
public class AES {

 private static SecretKeySpec secretKey;
 private static final String VK_secretKey = "VaquarKhan-secrate-key!!!!";
 private static byte[] key;

 /**
 * 
 * @param myKey
 */
 public static void setKey(String myKey) {
 MessageDigest sha = null;
 try {
 key = myKey.getBytes("UTF-8");
 sha = MessageDigest.getInstance("SHA-1");
 key = sha.digest(key);
 key = Arrays.copyOf(key, 16);
 secretKey = new SecretKeySpec(key, "AES");
 } catch (NoSuchAlgorithmException e) {
 e.printStackTrace();
 } catch (UnsupportedEncodingException e) {
 e.printStackTrace();
 }
 }
/**
 * encrypt
 * @param strToEncrypt
 * @param secret
 * @return
 */
 public static String encrypt(String strToEncrypt, String secret) {
 try {
 setKey(secret);
 Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
 cipher.init(Cipher.ENCRYPT_MODE, secretKey);
 return Base64.getEncoder().encodeToString(cipher.doFinal(strToEncrypt.getBytes("UTF-8")));
 } catch (Exception e) {
 System.out.println("Error while encrypting: " + e.toString());
 }
 return null;
 }
/**
 * decrypt
 * @param strToDecrypt
 * @param secret
 * @return
 */
 public static String decrypt(String strToDecrypt, String secret) {
 try {
 setKey(secret);
 Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5PADDING");
 cipher.init(Cipher.DECRYPT_MODE, secretKey);
 return new String(cipher.doFinal(Base64.getDecoder().decode(strToDecrypt)));
 } catch (Exception e) {
 System.out.println("Error while decrypting: " + e.toString());
 }
 return null;
 }

 public static void main(String[] args) {
 final String secretKey = VK_secretKey;
 String password = "VKhan@12";
 //
 String encryptedString = AES.encrypt(password, secretKey);
 String decryptedString = AES.decrypt(encryptedString, secretKey);
 //
 System.out.println(password);
 System.out.println(encryptedString);
 System.out.println(decryptedString);
 }

}
</code></pre>

I have an image that is Base64 encoded. What is the best way to decode that in Java? Hopefully using only the libraries included with Sun Java 6.

Decode Base64 data in Java

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我有一个Base64编码的图像。在Java中解码它的最好方法是什么？希望只使用Sun Java6附带的库。

问在Java中解码Base64数据
EN

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