com.hp.util.ip

Class DnsName

java.lang.Object

com.hp.util.cache.CacheableDataType

com.hp.util.ip.DnsName

All Implemented Interfaces:

Serializable, Comparable<DnsName>

public final class DnsName
extends CacheableDataType
implements Comparable<DnsName>

Represents a DNS name.

All constructors for this class are private. Creating instances of DnsName is done via the static valueOf(java.lang.String) methods on the class. Note that a special value representing "Unresolvable" can be obtained via the UNRESOLVABLE public field.

Instances of this class are immutable, making them inherently threadsafe.

This class overrides equals(java.lang.Object) and hashCode() so that instances play nicely with the Collection classes.

Implements the Comparable interface to ensure that a sorted list of DnsNames is presented in an intuitive order. In particular, case is ignored, and numeric suffixes are taken into account. Also note that "Unresolvable" instances are sorted to the end of the list. For example:

• switch1.cup.hp.com
• switch1.rose.hp.com
• switch3.cup.hp.com
• switch3.rose.hp.com
• switch4.rose.hp.com
• switch13.rose.hp.com
• switch14.rose.hp.com
• switch22.rose.hp.com
• switch23.rose.hp.com
• zodiac.rose.hp.com
• (Unresolvable DNS Name)
• (Unresolvable DNS Name)

Author:

Simon Hunt

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
static DnsName	UNRESOLVABLE Our instance that represents an unresolvable DNS name.

Method Summary

Methods

Modifier and Type	Method and Description
int	compareTo(DnsName other) Overridden to (a) ignore case, and (b) take embedded numbers into account.
static DnsName	dns(String s) Convenience method that simply delegates to valueOf(String).
boolean	equals(Object o)
String	getDomainName() Returns the domain name; that is, everything after the first dot.
String	getHostName() Returns the host name; that is, everything up to (but not including) the first dot.
int	hashCode()
boolean	isUnresolvable() Returns true if this instance is the "unresolvable" instance.
String	toString()
static DnsName	valueOf(String s) Returns an object that represents the value of the DNS name identified by the specified string.

Methods inherited from class com.hp.util.cache.CacheableDataType

getRefQ, keyFromBytes

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

UNRESOLVABLE

public static final DnsName UNRESOLVABLE

Our instance that represents an unresolvable DNS name.

Method Detail

getHostName

public String getHostName()

Returns the host name; that is, everything up to (but not including) the first dot.

Returns:

the host name portion

getDomainName

public String getDomainName()

Returns the domain name; that is, everything after the first dot.

Returns:

the domain name portion

toString

public String toString()

Overrides:

toString in class Object

isUnresolvable

public boolean isUnresolvable()

Returns true if this instance is the "unresolvable" instance.

Returns:

true if this is the "unresolvable" instance

compareTo

public int compareTo(DnsName other)

Overridden to (a) ignore case, and (b) take embedded numbers into account. Note that UNRESOLVABLE instances will sort to the end.

Specified by:

compareTo in interface Comparable<DnsName>

Parameters:

other - the other instance we are comparing to

Returns:

a number less than, equal to, or greater than zero as this instance is earlier than, the same as, or later than the other in natural sort order

equals

public boolean equals(Object o)

Note that this comparison ignores case.

Overrides:

equals in class Object

Parameters:

o - the other instance to compare to

Returns:

true if this instance is equivalent to the specified instance

hashCode

public int hashCode()

Overrides:

hashCode in class Object

valueOf

public static DnsName valueOf(String s)

Returns an object that represents the value of the DNS name identified by the specified string. Note that the string is trimmed of whitespace first.

If the parameter is an empty string ("") then the instance representing "unresolvable DNS name" is returned instead.

Parameters:

s - the string representation of the DNS name

Returns:

an object representing the specified DNS name

Throws:

NullPointerException - if the string is null

dns

public static DnsName dns(String s)

Convenience method that simply delegates to valueOf(String). Note that code can be written more concisely by using a static import of this method; for example, the following two statements are equivalent:

 DnsName a = DnsName.valueOf("foo.hp.com");
 DnsName a = dns("foo.hp.com");
 

Parameters:

s - the string representation of the DNS name

Returns:

an object representing the specified DNS name

Throws:

NullPointerException - if the string is null