- All Implemented Interfaces:
- Serializable
UID represents an identifier that is unique over time
 with respect to the host it is generated on, or one of 216
 "well-known" identifiers.
 The UID() constructor can be used to generate an
 identifier that is unique over time with respect to the host it is
 generated on.  The UID(short) constructor can be used to
 create one of 216 well-known identifiers.
 
A UID instance contains three primitive values:
 
- unique, an- intthat uniquely identifies the VM that this- UIDwas generated in, with respect to its host and at the time represented by the- timevalue (an example implementation of the- uniquevalue would be a process identifier), or zero for a well-known- UID
- time, a- longequal to a time (as returned by- System.currentTimeMillis()) at which the VM that this- UIDwas generated in was alive, or zero for a well-known- UID
- count, a- shortto distinguish- UIDs generated in the same VM with the same- timevalue
An independently generated UID instance is unique
 over time with respect to the host it is generated on as long as
 the host requires more than one millisecond to reboot and its system
 clock is never set backward.  A globally unique identifier can be
 constructed by pairing a UID instance with a unique host
 identifier, such as an IP address.
- Since:
- 1.1
- See Also:
- 
Constructor SummaryConstructors
- 
Method SummaryModifier and TypeMethodDescriptionbooleanCompares the specified object with thisUIDfor equality.inthashCode()Returns the hash code value for thisUID.static UIDConstructs and returns a newUIDinstance by unmarshalling a binary representation from anDataInputinstance.toString()Returns a string representation of thisUID.voidwrite(DataOutput out) Marshals a binary representation of thisUIDto aDataOutputinstance.
- 
Constructor Details- 
UIDpublic UID()Generates aUIDthat is unique over time with respect to the host that it was generated on.
- 
UIDpublic UID(short num) Creates a "well-known"UID. There are 216 possible such well-known ids.A UIDcreated via this constructor will not clash with anyUIDs generated via the no-arg constructor.- Parameters:
- num- number for well-known- UID
 
 
- 
- 
Method Details- 
hashCodepublic int hashCode()Returns the hash code value for thisUID.
- 
equalsCompares the specified object with thisUIDfor equality. This method returnstrueif and only if the specified object is aUIDinstance with the sameunique,time, andcountvalues as this one.
- 
toStringReturns a string representation of thisUID.
- 
writeMarshals a binary representation of thisUIDto aDataOutputinstance.Specifically, this method first invokes the given stream's DataOutput.writeInt(int)method with thisUID'suniquevalue, then it invokes the stream'sDataOutput.writeLong(long)method with thisUID'stimevalue, and then it invokes the stream'sDataOutput.writeShort(int)method with thisUID'scountvalue.- Parameters:
- out- the- DataOutputinstance to write this- UIDto
- Throws:
- IOException- if an I/O error occurs while performing this operation
 
- 
readConstructs and returns a newUIDinstance by unmarshalling a binary representation from anDataInputinstance.Specifically, this method first invokes the given stream's DataInput.readInt()method to read auniquevalue, then it invoke's the stream'sDataInput.readLong()method to read atimevalue, then it invoke's the stream'sDataInput.readShort()method to read acountvalue, and then it creates and returns a newUIDinstance that contains theunique,time, andcountvalues that were read from the stream.- Parameters:
- in- the- DataInputinstance to read- UIDfrom
- Returns:
- unmarshalled UIDinstance
- Throws:
- IOException- if an I/O error occurs while performing this operation
 
 
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