Ho appena implementato questa classe di utilità che crea UUID come String con o senza trattini . Sentitevi liberi di usare e condividere. Spero che sia d'aiuto!
package your.package.name;
import java.security.SecureRandom;
import java.util.Random;
/**
* Utility class that creates random-based UUIDs.
*
*/
public abstract class RandomUuidStringCreator {
private static final int RANDOM_VERSION = 4;
/**
* Returns a random-based UUID as String.
*
* It uses a thread local {@link SecureRandom}.
*
* @return a random-based UUID string
*/
public static String getRandomUuid() {
return getRandomUuid(SecureRandomLazyHolder.SECURE_RANDOM);
}
/**
* Returns a random-based UUID as String WITH dashes.
*
* It uses a thread local {@link SecureRandom}.
*
* @return a random-based UUID string
*/
public static String getRandomUuidWithDashes() {
return format(getRandomUuid());
}
/**
* Returns a random-based UUID String.
*
* It uses any instance of {@link Random}.
*
* @return a random-based UUID string
*/
public static String getRandomUuid(Random random) {
long msb = 0;
long lsb = 0;
// (3) set all bit randomly
if (random instanceof SecureRandom) {
// Faster for instances of SecureRandom
final byte[] bytes = new byte[16];
random.nextBytes(bytes);
msb = toNumber(bytes, 0, 8); // first 8 bytes for MSB
lsb = toNumber(bytes, 8, 16); // last 8 bytes for LSB
} else {
msb = random.nextLong(); // first 8 bytes for MSB
lsb = random.nextLong(); // last 8 bytes for LSB
}
// Apply version and variant bits (required for RFC-4122 compliance)
msb = (msb & 0xffffffffffff0fffL) | (RANDOM_VERSION & 0x0f) << 12; // apply version bits
lsb = (lsb & 0x3fffffffffffffffL) | 0x8000000000000000L; // apply variant bits
// Convert MSB and LSB to hexadecimal
String msbHex = zerofill(Long.toHexString(msb), 16);
String lsbHex = zerofill(Long.toHexString(lsb), 16);
// Return the UUID
return msbHex + lsbHex;
}
/**
* Returns a random-based UUID as String WITH dashes.
*
* It uses a thread local {@link SecureRandom}.
*
* @return a random-based UUID string
*/
public static String getRandomUuidWithDashes(Random random) {
return format(getRandomUuid(random));
}
private static long toNumber(final byte[] bytes, final int start, final int length) {
long result = 0;
for (int i = start; i < length; i++) {
result = (result << 8) | (bytes[i] & 0xff);
}
return result;
}
private static String zerofill(String string, int length) {
return new String(lpad(string.toCharArray(), length, '0'));
}
private static char[] lpad(char[] chars, int length, char fill) {
int delta = 0;
int limit = 0;
if (length > chars.length) {
delta = length - chars.length;
limit = length;
} else {
delta = 0;
limit = chars.length;
}
char[] output = new char[chars.length + delta];
for (int i = 0; i < limit; i++) {
if (i < delta) {
output[i] = fill;
} else {
output[i] = chars[i - delta];
}
}
return output;
}
private static String format(String string) {
char[] input = string.toCharArray();
char[] output = new char[36];
System.arraycopy(input, 0, output, 0, 8);
System.arraycopy(input, 8, output, 9, 4);
System.arraycopy(input, 12, output, 14, 4);
System.arraycopy(input, 16, output, 19, 4);
System.arraycopy(input, 20, output, 24, 12);
output[8] = '-';
output[13] = '-';
output[18] = '-';
output[23] = '-';
return new String(output);
}
// Holds lazy secure random
private static class SecureRandomLazyHolder {
static final Random SECURE_RANDOM = new SecureRandom();
}
/**
* For tests!
*/
public static void main(String[] args) {
System.out.println("// Using `java.security.SecureRandom` (DEFAULT)");
System.out.println("RandomUuidCreator.getRandomUuid()");
System.out.println();
for (int i = 0; i < 5; i++) {
System.out.println(RandomUuidStringCreator.getRandomUuid());
}
System.out.println();
System.out.println("// Using `java.util.Random` (FASTER)");
System.out.println("RandomUuidCreator.getRandomUuid(new Random())");
System.out.println();
Random random = new Random();
for (int i = 0; i < 5; i++) {
System.out.println(RandomUuidStringCreator.getRandomUuid(random));
}
}
}
Questo è l'output:
// Using `java.security.SecureRandom` (DEFAULT)
RandomUuidStringCreator.getRandomUuid()
'f553ca75657b4b5d85bedf1082785a0b'
'525ecc389e934f209b97d0f0db09d9c6'
'93ec6425bb04499ab47b790fd013ab0d'
'c2d438c620ea4cd5baafd448f9fe945b'
'fb4bc5734931415e94e78da62cb5fe0d'
// Using `java.util.Random` (FASTER)
RandomUuidStringCreator.getRandomUuid(new Random())
'051360b5c92d40fbbb89b40842adbacc'
'a993896538aa43faacbcfd83f913f38b'
'720684d22c584d5299cb03cdbc1912d2'
'82cf94ea296a4a138a92825a0068d4a1'
'a7eda46a215c4e55be3aa957ba74ca9c'