java 加密算法 base64

    <span style="color: #464646; font-family: simsun; font-size: 14px; line-height: 21px; background-color: #ffffff;">自己写加密算法</span>

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import java.io.UnsupportedEncodingException;

public class Base64 {
    private static char[] base64EncodeChars = new char[]{
            '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', '+', '/'};
    private static byte[] base64DecodeChars = new byte[]{
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
            52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,
            -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
            15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
            -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
            41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1};
   
    public static String encode(byte[] data) {
        StringBuffer sb = new StringBuffer();
        int len = data.length;
        int i = 0;
        int b1, b2, b3;
        while (i < len) {
            b1 = data[i++] &amp; 0xff;
            if (i == len) {
                sb.append(base64EncodeChars[b1 >>> 2]);
                sb.append(base64EncodeChars[(b1 &amp; 0x3) << 4]);
                sb.append("==");
                break;
            }
            b2 = data[i++] &amp; 0xff;
            if (i == len) {
                sb.append(base64EncodeChars[b1 >>> 2]);
                sb.append(base64EncodeChars[((b1 &amp; 0x03) << 4) | ((b2 &amp; 0xf0) >>> 4)]);
                sb.append(base64EncodeChars[(b2 &amp; 0x0f) << 2]);
                sb.append("=");
                break;
            }
            b3 = data[i++] &amp; 0xff;
            sb.append(base64EncodeChars[b1 >>> 2]);
            sb.append(base64EncodeChars[((b1 &amp; 0x03) << 4) | ((b2 &amp; 0xf0) >>> 4)]);
            sb.append(base64EncodeChars[((b2 &amp; 0x0f) << 2) | ((b3 &amp; 0xc0) >>> 6)]);
            sb.append(base64EncodeChars[b3 &amp; 0x3f]);
        }
        return sb.toString();
    }
   
    public static byte[] decode(String str) throws UnsupportedEncodingException {
        StringBuffer sb = new StringBuffer();
        byte[] data = str.getBytes("US-ASCII");
        int len = data.length;
        int i = 0;
        int b1, b2, b3, b4;
        while (i < len) {
           
            do {
                b1 = base64DecodeChars[data[i++]];
            } while (i < len &amp;&amp; b1 == -1);
            if (b1 == -1) break;
           
            do {
                b2 = base64DecodeChars
                        [data[i++]];
            } while (i < len &amp;&amp; b2 == -1);
            if (b2 == -1) break;
            sb.append((char) ((b1 << 2) | ((b2 &amp; 0x30) >>> 4)));
           
            do {
                b3 = data[i++];
                if (b3 == 61) return sb.toString().getBytes("iso8859-1");
                b3 = base64DecodeChars[b3];
            } while (i < len &amp;&amp; b3 == -1);
            if (b3 == -1) break;
            sb.append((char) (((b2 &amp; 0x0f) << 4) | ((b3 &amp; 0x3c) >>> 2)));
           
            do {
                b4 = data[i++];
                if (b4 == 61) return sb.toString().getBytes("iso8859-1");
                b4 = base64DecodeChars[b4];
            } while (i < len &amp;&amp; b4 == -1);
            if (b4 == -1) break;
            sb.append((char) (((b3 &amp; 0x03) << 6) | b4));
        }
        return sb.toString().getBytes("iso8859-1");
    }
    public static void main(String[] args) throws UnsupportedEncodingException {
        String s = "abcd";
        System.out.println("加密前：" + s);
        String x = encode(s.getBytes());
        System.out.println("加密后：" + x);
        String x1 = new String(decode(x));
        System.out.println("解密后：" + x1);
    }
}

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