- java.lang.Object
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- java.rmi.server.UID
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- All Implemented Interfaces:
Serializable
public final class UID extends Object implements Serializable
AUIDrepresents 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. TheUID(short)constructor can be used to create one of 216 well-known identifiers.A
UIDinstance contains three primitive values:unique, anintthat uniquely identifies the VM that thisUIDwas generated in, with respect to its host and at the time represented by thetimevalue (an example implementation of theuniquevalue would be a process identifier), or zero for a well-knownUIDtime, alongequal to a time (as returned bySystem.currentTimeMillis()) at which the VM that thisUIDwas generated in was alive, or zero for a well-knownUIDcount, ashortto distinguishUIDs generated in the same VM with the sametimevalue
An independently generated
UIDinstance 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 aUIDinstance with a unique host identifier, such as an IP address.- Since:
- 1.1
- See Also:
- Serialized Form
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description booleanequals(Object obj)Compares the specified object with thisUIDfor equality.inthashCode()Returns the hash code value for thisUID.static UIDread(DataInput in)Constructs and returns a newUIDinstance by unmarshalling a binary representation from anDataInputinstance.StringtoString()Returns a string representation of thisUID.voidwrite(DataOutput out)Marshals a binary representation of thisUIDto aDataOutputinstance.
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Constructor Detail
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UID
public UID()
Generates aUIDthat is unique over time with respect to the host that it was generated on.
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UID
public 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-knownUID
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Method Detail
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hashCode
public int hashCode()
Returns the hash code value for thisUID.- Overrides:
hashCodein classObject- Returns:
- the hash code value for this
UID - See Also:
Object.equals(java.lang.Object)
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equals
public boolean equals(Object obj)
Compares 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.- Overrides:
equalsin classObject- Parameters:
obj- the object to compare thisUIDto- Returns:
trueif the given object is equivalent to this one, andfalseotherwise- See Also:
Object.hashCode()
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toString
public String toString()
Returns a string representation of thisUID.
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write
public void write(DataOutput out) throws IOException
Marshals 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- theDataOutputinstance to write thisUIDto- Throws:
IOException- if an I/O error occurs while performing this operation
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read
public static UID read(DataInput in) throws IOException
Constructs 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- theDataInputinstance to readUIDfrom- Returns:
- unmarshalled
UIDinstance - Throws:
IOException- if an I/O error occurs while performing this operation
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