android 类型转换,android 类型转换 工具函数

android中类型转换好像支持不是太好，备份下有用的类型转换函数和工具函数.

一、类型转换

1.byte 转 int   ( int 可以再转成long double float )

[java]

public static int byteToInt(byte[] data, int offset)

{

int result = 0;

int n1, n2, n3, n4;

n1 = data[offset + 3] & 0xFF;

n2 = data[offset + 2] & 0xFF;

n3 = data[offset + 1] & 0xFF;

n4 = data[offset] & 0xFF;

result = n1 << 24  | n2 << 16 | n3 << 8 | n4;

return result;

}

2. byte 转 Hex

[java] www.2cto.com

public static String toHexString(byte[] b)

{

char HEX_DIGITS[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',

'A', 'B', 'C', 'D', 'E', 'F' };

StringBuilder sb = new StringBuilder(b.length * 2);

for (int i = 0; i < b.length; i++)

{

sb.append(HEX_DIGITS[(b[i] & 0xf0) >> 4]);

sb.append(HEX_DIGITS[b[i] & 0x0f]);

}

return sb.toString();

}

3. HexString 转 long

[java]

public static long hexStringToLong(String s)

{

String serial = "0123456789ABCDEF";

s = s.trim().toUpperCase();

if( s.length() > 8 ) return 0;

long num = 0;

int  len = s.length();

for( int i = 0; i < len; i++)

{

num += (serial.indexOf( s.charAt(i) ) << (4 * (len - i - 1)));

}

return num;

}

二、 工具函数

1. md5sum

[java]

public static String getMd5sum(String filename)

{

InputStream fis;

byte[] buffer = new byte[1024];

int numRead = 0;

MessageDigest md5;

try{

fis = new FileInputStream(filename);

md5 = MessageDigest.getInstance("MD5");

while((numRead=fis.read(buffer)) > 0) {

md5.update(buffer,0,numRead);

}

fis.close();

return toHexString(md5.digest());

} catch (Exception e) {

return null;

}

}