java 5 和java 6里已带相应的类 java.util.UUID, 直接调用即可:
System.out.println( java.util.UUID.randomUUID());
但如果用java 1.4怎么办呢,其实这个类相关很少,可以用jdk5里拿出来,放到java 1.4里面用。从中也可以看出GUID生成的算法。不错吧?
源码需要稍做修改如下:
import java.io.*;
import java.security.*;
public final class UUID
implements Serializable, Comparable
{
private UUID(byte abyte0[])
{
version = -1;
variant = -1;
timestamp = -1L;
sequence = -1;
node = -1L;
hashCode = -1;
long l = 0L;
long l1 = 0L;
// if(!$assertionsDisabled && abyte0.length != 16)
// throw new AssertionError();
for(int i = 0; i < 8; i++)
l = l << 8 | (long)(abyte0[i] & 0xff);
for(int j = 8; j < 16; j++)
l1 = l1 << 8 | (long)(abyte0[j] & 0xff);
mostSigBits = l;
leastSigBits = l1;
}
public UUID(long l, long l1)
{
version = -1;
variant = -1;
timestamp = -1L;
sequence = -1;
node = -1L;
hashCode = -1;
mostSigBits = l;
leastSigBits = l1;
}
public static UUID randomUUID()
{
SecureRandom securerandom = numberGenerator;
if(securerandom == null)
numberGenerator = securerandom = new SecureRandom();
byte abyte0[] = new byte[16];
securerandom.nextBytes(abyte0);
abyte0[6] &= 0xf;
abyte0[6] |= 0x40;
abyte0[8] &= 0x3f;
abyte0[8] |= 0x80;
UUID uuid = new UUID(abyte0);
return new UUID(abyte0);
}
public static UUID nameUUIDFromBytes(byte abyte0[])
{
MessageDigest messagedigest;
try
{
messagedigest = MessageDigest.getInstance("MD5");
}
catch(NoSuchAlgorithmException nosuchalgorithmexception)
{
throw new InternalError("MD5 not supported");
}
byte abyte1[] = messagedigest.digest(abyte0);
abyte1[6] &= 0xf;
abyte1[6] |= 0x30;
abyte1[8] &= 0x3f;
abyte1[8] |= 0x80;
return new UUID(abyte1);
}
public static UUID fromString(String s)
{
String as[] = s.split("-");
if(as.length != 5)
throw new IllegalArgumentException((new StringBuilder())
.append("Invalid UUID string: ").append(s).toString());
for(int i = 0; i < 5; i++)
as[i] = (new StringBuilder()).append("0x").append(as[i]).toString();
long l = Long.decode(as[0]).longValue();
l <<= 16;
l |= Long.decode(as[1]).longValue();
l <<= 16;
l |= Long.decode(as[2]).longValue();
long l1 = Long.decode(as[3]).longValue();
l1 <<= 48;
l1 |= Long.decode(as[4]).longValue();
return new UUID(l, l1);
}
public long getLeastSignificantBits()
{
return leastSigBits;
}
public long getMostSignificantBits()
{
return mostSigBits;
}
public int version()
{
if(version < 0)
version = (int)(mostSigBits >> 12 & 15L);
return version;
}
public int variant()
{
if(variant < 0)
if(leastSigBits >>> 63 == 0L)
variant = 0;
else
if(leastSigBits >>> 62 == 2L)
variant = 2;
else
variant = (int)(leastSigBits >>> 61);
return variant;
}
public long timestamp()
{
if(version() != 1)
throw new UnsupportedOperationException("Not a time-based UUID");
long l = timestamp;
if(l < 0L)
{
l = (mostSigBits & 4095L) << 48;
l |= (mostSigBits >> 16 & 65535L) << 32;
l |= mostSigBits >>> 32;
timestamp = l;
}
return l;
}
public int clockSequence()
{
if(version() != 1)
throw new UnsupportedOperationException("Not a time-based UUID");
if(sequence < 0)
sequence = (int)((leastSigBits & 0x3fff000000000000L) >>> 48);
return sequence;
}
public long node()
{
if(version() != 1)
throw new UnsupportedOperationException("Not a time-based UUID");
if(node < 0L)
node = leastSigBits & 0xffffffffffffL;
return node;
}
public String toString()
{
return (new StringBuilder()).append(digits(mostSigBits >> 32, 8)).append("-").append(digits(mostSigBits >> 16, 4))
.append("-").append(digits(mostSigBits, 4)).append("-")
.append(digits(leastSigBits >> 48, 4)).append("-").append(digits(leastSigBits, 12)).toString();
}
private static String digits(long l, int i)
{
long l1 = 1L << i * 4;
return Long.toHexString(l1 | l & l1 - 1L).substring(1);
}
public int hashCode()
{
if(hashCode == -1)
hashCode = (int)(mostSigBits >> 32 ^ mostSigBits ^ leastSigBits >> 32 ^ leastSigBits);
return hashCode;
}
public boolean equals(Object obj)
{
if(!(obj instanceof UUID))
return false;
if(((UUID)obj).variant() != variant())
{
return false;
} else
{
UUID uuid = (UUID)obj;
return mostSigBits == uuid.mostSigBits && leastSigBits == uuid.leastSigBits;
}
}
public int compareTo(UUID uuid)
{
return mostSigBits >= uuid.mostSigBits ? mostSigBits <= uuid.mostSigBits ?
leastSigBits >= uuid.leastSigBits ?
((byte) (((byte)(leastSigBits <= uuid.leastSigBits ? 0 : 1)))) : -1 : 1 : -1;
}
private void readObject(ObjectInputStream objectinputstream)
throws IOException, ClassNotFoundException
{
objectinputstream.defaultReadObject();
version = -1;
variant = -1;
timestamp = -1L;
sequence = -1;
node = -1L;
hashCode = -1;
}
public int compareTo(Object obj)
{
return compareTo((UUID)obj);
}
private static final long serialVersionUID = 0xbc9903f7986d852fL;
private final long mostSigBits;
private final long leastSigBits;
private transient int version;
private transient int variant;
private volatile transient long timestamp;
private transient int sequence;
private transient long node;
private transient int hashCode;
private static volatile SecureRandom numberGenerator = null;
// static final boolean $assertionsDisabled = !UUID.desiredAssertionStatus();
}