java做base64编码和解码（无须引用任何类库），,如下代码不依赖任何类库实

java做base64编码和解码（无须引用任何类库），,如下代码不依赖任何类库实

如下代码不依赖任何类库实现base64的编码和解码。

public class Base64Util {    private final static char[] ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".toCharArray();    private static int[]  toInt   = new int[128];    static {        for(int i=0; i< 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 < size){            byte b0 = buf[i++];            byte b1 = (i < size) ? buf[i++] : 0;            byte b2 = (i < size) ? buf[i++] : 0;            int mask = 0x3F;            ar[a++] = ALPHABET[(b0 >> 2) & mask];            ar[a++] = ALPHABET[((b0 << 4) | ((b1 & 0xFF) >> 4)) & mask];            ar[a++] = ALPHABET[((b1 << 2) | ((b2 & 0xFF) >> 6)) & mask];            ar[a++] = ALPHABET[b2 & 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< s.length(); i+=4){            int c0 = toInt[s.charAt( i )];            int c1 = toInt[s.charAt( i + 1)];            buffer[index++]= (byte)(((c0 << 2) | (c1 >> 4)) & mask);            if(index >= buffer.length){                return buffer;            }            int c2 = toInt[s.charAt( i + 2)];            buffer[index++]= (byte)(((c1 << 4) | (c2 >> 2)) & mask);            if(index >= buffer.length){                return buffer;            }            int c3 = toInt[s.charAt( i + 3 )];            buffer[index++]= (byte)(((c2 << 6) | c3) & mask);        }        return buffer;    } }