algorithm base64 encode byte array to string - Android File Input Output

Android examples for File Input Output:Base64

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Description

algorithm base64 encode byte array to string

Demo Code


//package com.java2s;

public class Main {
    public static String encode(byte[] bytes) {
        if (bytes == null) {
            return null;
        }/*from   w  w w .ja  v a  2 s.  co m*/
        if (bytes.length == 0) {
            return "";
        }

        int groupCount = bytes.length / 3;

        StringBuffer resultBuffer = new StringBuffer();

        byte bufferByte = 0;
        for (int i = 0; i < groupCount; i++) {
            int startIndex = i * 3;

            bufferByte = (byte) (bytes[startIndex] >> 2);
            resultBuffer.append(encodeBase64Byte(bufferByte));

            bufferByte = (byte) (((bytes[startIndex] & 0x03) << 4) | (bytes[startIndex + 1] >> 4));
            resultBuffer.append(encodeBase64Byte(bufferByte));

            bufferByte = (byte) (((bytes[startIndex + 1] & 0x0F) << 2) | (bytes[startIndex + 2] >> 6));
            resultBuffer.append(encodeBase64Byte(bufferByte));

            bufferByte = (byte) (bytes[startIndex + 2] & 0x3F);
            resultBuffer.append(encodeBase64Byte(bufferByte));
        }

        if ((bytes.length - (groupCount * 3)) == 2) {
            resultBuffer.append(encodeLast2Bytes(bytes));
        }

        if ((bytes.length - (groupCount * 3)) == 1) {
            resultBuffer.append(encodeLast1Byte(bytes));
        }

        return resultBuffer.toString();
    }

    private static char encodeBase64Byte(byte base64Byte) {
        if ((base64Byte >= 0) && (base64Byte <= 25)) {
            return (char) (base64Byte + 65);
        } else if ((base64Byte >= 26) && (base64Byte <= 51)) {
            return (char) (base64Byte - 26 + 97);
        } else if ((base64Byte >= 52) && (base64Byte <= 61)) {
            return (char) (base64Byte - 52 + 48);
        } else if (base64Byte == 62) {
            return '+';
        } else if (base64Byte == 63) {
            return '/';
        } else {
            return '0';
        }
    }

    private static String encodeLast2Bytes(byte bytes[]) {
        byte firstByte = bytes[bytes.length - 2];
        byte secondByte = bytes[bytes.length - 1];

        StringBuffer resultBuffer = new StringBuffer();

        byte bufferByte = 0;

        bufferByte = (byte) (firstByte >> 2);
        resultBuffer.append(encodeBase64Byte(bufferByte));

        bufferByte = (byte) (((firstByte & 0x03) << 4) | (secondByte >> 4));
        resultBuffer.append(encodeBase64Byte(bufferByte));

        bufferByte = (byte) ((secondByte & 0x0F) << 2);
        resultBuffer.append(encodeBase64Byte(bufferByte));

        resultBuffer.append('=');

        return resultBuffer.toString();
    }

    private static String encodeLast1Byte(byte bytes[]) {
        byte lastByte = bytes[bytes.length - 1];

        StringBuffer resultBuffer = new StringBuffer();

        byte bufferByte = 0;

        bufferByte = (byte) (lastByte >> 2);
        resultBuffer.append(encodeBase64Byte(bufferByte));

        bufferByte = (byte) ((lastByte & 0x03) << 4);
        resultBuffer.append(encodeBase64Byte(bufferByte));

        resultBuffer.append('=');
        resultBuffer.append('=');

        return resultBuffer.toString();
    }
}

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