Base64位解密算法

package mains;


/***
 * Base64位解密算法
 * @author Administrator xlaohe1
 *
 */
public class Base64Decrypt {

	/**
	 * 64位字符
	 */
	private final static String Base64Ret = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

	/**
	 * 放入加密的字符转换为二进制
	 * @author Administrator xlaohe1
	 * 
	 * @param str 加密后的字符
	 * @return 加密后的字符的ascii码的二进制
	 */
	private static String getAsciiByPWD(String str) {
		str = str.replaceAll("=", "");
		String ss = "";
		for (int i = 0; i < str.length(); i++) {
			String s = Integer.toBinaryString(
					Base64Ret.indexOf(str.substring(i, i + 1))); // 转换为二进制
			int slen = s.length();
			if (slen < 6)
				for (int l = 0; l < 6 - slen; l++)
					s = "0" + s; // 不足6位+0
			ss += s;
		}
		return ss.substring(0, ss.length() - ss.length() % 8); // 因为base64是8字节,不足加的0,所以多出来的舍弃
	}

	/**
	 * 二进制转换为ascii码
	 * @author Administrator xlaohe1
	 * 
	 * @param str getAsciiByPWD后的二进制
	 */
	private static void TwoToASCII(String str) {
		// String str = "011011010110010101101101";
		System.out.print((char) Integer.parseInt(Integer.valueOf(
				str.substring(0, 8), 2).toString())); // 这里输出的就是解密后的字符串
		str = str.substring(8);
		if (str.length() != 0)
			TwoToASCII(str);
	}

	public static void main(String args[]) throws Exception {
               try{
		String str = "TWFuIGlzIGRpc3Rpbmd1aXNoZWQsIG5vdCBvbmx5IGJ5IGhpcyByZWFzb24sIGJ1dCBieSB0aGlzIHNpbmd1bGFyIHBhc3Npb24gZnJvbSBvdGhlciBhbmltYWxzLCB3aGljaCBpcyBhIGx1c3Qgb2YgdGhlIG1pbmQsIHRoYXQgYnkgYSBwZXJzZXZlcmFuY2Ugb2YgZGVsaWdodCBpbiB0aGUgY29udGludWVkIGFuZCBpbmRlZmF0aWdhYmxlIGdlbmVyYXRpb24gb2Yga25vd2xlZGdlLCBleGNlZWRzIHRoZSBzaG9ydCB2ZWhlbWVuY2Ugb2YgYW55IGNhcm5hbCBwbGVhc3VyZS4=";
		String slst = getAsciiByPWD(str);// bWVt==
		System.out.println(slst);
		TwoToASCII(slst);
		System.out.println();
}catch(Exception e) {
  System.out.println("输入错误");
}
		//输出结果为:Man is distinguished, not only by his reason, but by this singular passion from other animals, which is a lust of the mind, that by a perseverance of delight in the continued and indefatigable generation of knowledge, exceeds the short vehemence of any carnal pleasure.
	}

	
}