UUID生成工具

public class UUIDUtils {
private static SecureRandom SEEDER_STATIC = null;
private static byte[] ADDRESS = null;
private static String MID_VALUE_STATIC = null;
private String midValue = null;
private SecureRandom seeder = null;

static {
try {
ADDRESS = InetAddress.getLocalHost().getAddress();
StringBuffer buffer = new StringBuffer(8);
buffer.append(toHex(toInt(ADDRESS), 8));
MID_VALUE_STATIC = buffer.toString();
SEEDER_STATIC = new SecureRandom();
SEEDER_STATIC.nextInt();
} catch (Exception ex) {
ex.printStackTrace();
}
}

public UUIDUtils() {
StringBuffer buffer = new StringBuffer(16);
buffer.append(MID_VALUE_STATIC);
buffer.append(toHex(System.identityHashCode(this), 8));
midValue = buffer.toString();
seeder = new SecureRandom();
seeder.nextInt();
}

/**
* 该方法用来产生一个32位的唯一的标记String
*
* @param obj
* 传入一个参考的对象
* @return
*/
public static String generate(Object obj) {
StringBuffer uid = new StringBuffer(32);

// get the system time
long currentTimeMillis = System.currentTimeMillis();
uid.append(toHex((int) (currentTimeMillis & -1L), 8));

// get the internet address
uid.append(MID_VALUE_STATIC);

// get the object hash value
uid.append(toHex(System.identityHashCode(obj), 8));

// get the random number
uid.append(toHex(getRandom(), 8));

return uid.toString();
}

/**
* 该方法用来产生一个32位的String唯一标记
*/
public String generate() {
StringBuffer uid = new StringBuffer(32);

// get the system time
long currentTimeMillis = System.currentTimeMillis();
uid.append(toHex((int) (currentTimeMillis & -1L), 8));

// get the internet address
uid.append(midValue);

// get the random number
uid.append(toHex(seeder.nextInt(), 8));

return uid.toString();
}

private static String toHex(int value, int length) {
char[] hexDigits = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
StringBuffer buffer = new StringBuffer(length);
int shift = length - 1 << 2;
for (int i = -1; ++i < length;) {
buffer.append(hexDigits[value >> shift & 0xf]);
value <<= 4;
}

return buffer.toString();
}

private static int toInt(byte[] bytes) {
int value = 0;
for (int i = -1; ++i < bytes.length;) {
value <<= 8;
value |= bytes[i];
}

return value;
}

private static synchronized int getRandom() {
return SEEDER_STATIC.nextInt();
}