java.lang.Object java.rmi.server.UID
public final 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()
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 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 UID
s generated in the same VM with the same time
valueAn 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.
UID()
UID
that is unique over time with respect to the host that it was generated on. UID(short num)
UID
. Method Summary boolean
equals(Object obj)
UID
for equality. int
hashCode()
UID
. static UID
read(DataInput in)
UID
instance by unmarshalling a binary representation from an DataInput
instance. String
toString()
UID
. void
write(DataOutput out)
UID
to a DataOutput
instance. UID
public UID()
UID
that is unique over time with respect to the host that it was generated on.
public UID(short num)
UID
. There are 216 possible such well-known ids.
A UID
created via this constructor will not clash with any UID
s generated via the no-arg constructor.
num
- number for well-known UID
public int hashCode()
UID
.
hashCode
in class Object
UID
Object.equals(java.lang.Object)
, Hashtable
public boolean equals(Object obj)
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.
equals
in class Object
obj
- the object to compare this UID
to
true
if the given object is equivalent to this one, and false
otherwise
Object.hashCode()
, Hashtable
public String toString()
UID
.
toString
in class Object
UID
public void write(DataOutput out) throws IOException
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.
out
- the DataOutput
instance to write this UID
to
IOException
- if an I/O error occurs while performing this operation
public static UID read(DataInput in) throws IOException
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.
in
- the DataInput
instance to read UID
from
UID
instance
IOException
- if an I/O error occurs while performing this operation
Copyright © 2004, 2010 Oracle and/or its affiliates. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.
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