JAVA实现Base64转码

package cn.jsprun.utils;
import java.io.ByteArrayOutputStream;
import java.io.UnsupportedEncodingException;


public final class Base64 {
    private static final 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 final 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 final String encode(String str,String charsetName) {
    	return encode(str, charsetName,0);
    }
    public static final String encode(String str,String charsetName,int width) {
    	byte[] data = null;
		try {
			data = str.getBytes(charsetName);
		} catch (UnsupportedEncodingException e) {
			e.printStackTrace();
			return null;
		}
		int length=data.length;
		int size=(int)Math.ceil(length*1.36);
		int splitsize=width>0?size/width:0;
		StringBuffer sb = new StringBuffer(size+splitsize);
        int r = length % 3;
        int len = length - r;
        int i = 0;
        int c;
        while (i < len) {
            c = (0x000000ff & data[i++]) << 16 |
                (0x000000ff & data[i++]) << 8  |
                (0x000000ff & data[i++]);
            sb.append(base64EncodeChars[c >> 18]);
            sb.append(base64EncodeChars[c >> 12 & 0x3f]);
            sb.append(base64EncodeChars[c >> 6  & 0x3f]);
            sb.append(base64EncodeChars[c & 0x3f]);
        }
        if (r == 1) {
            c = 0x000000ff & data[i++];
            sb.append(base64EncodeChars[c >> 2]);
            sb.append(base64EncodeChars[(c & 0x03) << 4]);
            sb.append("==");
        }
        else if (r == 2) {
            c = (0x000000ff & data[i++]) << 8 |
                (0x000000ff & data[i++]);
            sb.append(base64EncodeChars[c >> 10]);
            sb.append(base64EncodeChars[c >> 4 & 0x3f]);
            sb.append(base64EncodeChars[(c & 0x0f) << 2]);
            sb.append("=");
        }
        if(splitsize>0){
        	char split='\n';
	        for(i=width;i<sb.length();i++){
	        	sb.insert(i, split);
	        	i+=width;
	        }
        }
        return sb.toString();
    }
    public static final String decode(String str,String charsetName) {
		byte[] data = null;
		try {
			data = str.getBytes(charsetName);
		} catch (UnsupportedEncodingException e) {
			e.printStackTrace();
			return null;
		}
        int len = data.length;
        ByteArrayOutputStream buf = new ByteArrayOutputStream((int)(len * 0.67));
        int i = 0;
        int b1, b2, b3, b4;
        while (i < len) {
            do {
            	if(i >= len){
            		b1 = -1;
            		break;
            	}
                b1 = base64DecodeChars[data[i++]];
            } while (i < len && b1 == -1);
            if (b1 == -1) {
                break;
            }
            do {
            	if(i >= len){
            		b2 = -1;
            		break;
            	}
                b2 = base64DecodeChars[data[i++]];
            } while (i < len && b2 == -1);
            if (b2 == -1) {
                break;
            }
            buf.write((int) ((b1 << 2) | ((b2 & 0x30) >>> 4)));
            do {
            	if(i >= len){
            		b3 = -1;
            		break;
            	}
                b3 = data[i++];
                if (b3 == 61) {
                	b3 = -1;
            		break;
                }
                b3 = base64DecodeChars[b3];
            } while (i < len && b3 == -1);
            if (b3 == -1) {
                break;
            }
            buf.write((int) (((b2 & 0x0f) << 4) | ((b3 & 0x3c) >>> 2)));
            do {
            	if(i >= len){
            		b4 = -1;
            		break;
            	}
                b4 = data[i++];
                if (b4 == 61) {
                	b4 = -1;
            		break;
                }
                b4 = base64DecodeChars[b4];
            } while (b4 == -1);
            if (b4 == -1) {
                break;
            }
            buf.write((int) (((b3 & 0x03) << 6) | b4));
        }
        try {
			return buf.toString(charsetName);
		} catch (UnsupportedEncodingException e) {
			e.printStackTrace();
			return null;
		}
    }
    
    
    public static void main(String[] args) {
		Base64 base = new Base64();
		String val = base.encode("你好","UTF-8");
		System.out.println(val);
		val = base.decode(val, "UTF-8");
		System.out.println(val);
	}
}

 

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