UID JDK 1.6)

Description

publicfinal class UID

A 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.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.UID(short) constructor can be used to create one of 2¹⁶ well-known identifiers.

A UID instance contains three primitive values:

unique, an int that uniquely identifies the VM that this UID was generated in, with respect to its host and at the time represented by the time value (an example implementation of the unique value would be a process identifier), or zero for a well-known UID
time, a long equal to a time (as returned by System.currentTimeMillis()) at which the VM that this UID was generated in was alive, or zero for a well-known UID
count, a short to distinguish UIDs generated in the same VM with the same time value

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.

See also:

Methods

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public boolean equals (Object obj)

Compares the specified object with this UID for equality.

Compares the specified object with this UID for
equality.

This method returns true if and only if the
specified object is a UID instance with the same
unique, time, and count
values as this one.
Returns: true if the given object is equivalent to this one, and false otherwise
Parameters:
- obj - the object to compare this UID to

public int hashCode ()

Returns the hash code value for this UID.

Returns the hash code value for this UID.
Returns: the hash code value for this UID

publicstatic UID read (DataInput in) throws IOException

Constructs and returns a new UID instance by unmarshalling a binary representation from an DataInput instance.

Specifically, this method first invokes the given stream's DataInput.readInt() method to read a unique value, then it invoke's the stream's DataInput.readLong() method to read a time value, then it invoke's the stream's DataInput.readShort() method to read a count value, and then it creates and returns a new UID instance that contains the unique, time, and count values that were read from the stream.
Returns: unmarshalled UID instance
Parameters:
- in - the DataInput instance to read UID from
Throws:
- IOException - if an I/O error occurs while performing this operation

public String toString ()

Returns a string representation of this UID.

Returns a string representation of this UID.
Returns: a string representation of this UID

public void write (DataOutput out) throws IOException

Marshals a binary representation of this UID to a DataOutput instance.

Specifically, this method first invokes the given stream's DataOutput.writeInt(int) method with this UID's unique value, then it invokes the stream's DataOutput.writeLong(long) method with this UID's time value, and then it invokes the stream's DataOutput.writeShort(int) method with this UID's count value.
Parameters:
- out - the DataOutput instance to write this UID to
Throws:
- IOException - if an I/O error occurs while performing this operation