com.portal.pfc.util

Class Pair

java.lang.Object

com.portal.pfc.util.Pair

All Implemented Interfaces:

Comparable

public class Pair
extends Object
implements Comparable

Utility class to hold a pair of objects that are related to each other. A typical use of this is where a Map or Set cannot be used to hold these pairs due to duplication of the key (really the primary value in the context of this class). Instead, a List can be used to hold instances of this class. Allows null values for both the primary and secondary objects.

An example use of this class could be to represent classification of hardware systems as an OS/Version pair of String objects.

Note: If instances of this class will be used in collection classes, you must make sure that the encapsulated primary and secondary objects implement the Comparable interface. In addition, it is recommended to have these classes also override equals() and hashCode() methods defined in class Object.

Author:

Madhu Narasimhan

See Also:

compareTo(Object)

Constructor Summary

Constructors

Constructor and Description
Pair() Constructs a Pair with primary and secondary objects set to null.
Pair(Object primary, Object secondary) Constructs a Pair with the given primary and secondary values.

Method Summary

Modifier and Type	Method and Description
int	compareTo(Object another) Compares this object with the specified object for order.
boolean	equals(Object object) Compares this Pair to the specified object.
Object	getPrimary() Returns the primary object
String	getPrimaryAsString() If the primary object is a String returns the String.
Object	getSecondary() Returns the secondary object
String	getSecondaryAsString() If the secondary object is a String returns the String.
int	hashCode() Returns a hash code value for the object.
void	setPrimary(Object primary) Sets the primary object to the given value
void	setSecondary(Object secondary) Sets the secondary object to the given value
String	toString() Returns a string form of the primary and secondary objects.

Methods inherited from class java.lang.Object

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

Constructor Detail

Pair

public Pair()

Constructs a Pair with primary and secondary objects set to null.

Pair

public Pair(Object primary,
            Object secondary)

Constructs a Pair with the given primary and secondary values.

Parameters:

primary - Primary value

secondary - Secondary value

Method Detail

getPrimary

public Object getPrimary()

Returns the primary object

Returns:

Primary object

getPrimaryAsString

public String getPrimaryAsString()

If the primary object is a String returns the String.

Parameters:

Primary - object as String or null if it's not a string.

setPrimary

public void setPrimary(Object primary)

Sets the primary object to the given value

Parameters:

primary - Primary object

getSecondary

public Object getSecondary()

Returns the secondary object

Returns:

Secondary object

getSecondaryAsString

public String getSecondaryAsString()

If the secondary object is a String returns the String.

Parameters:

Secondary - object as String or null if it's not a string.

setSecondary

public void setSecondary(Object secondary)

Sets the secondary object to the given value

Parameters:

secondary - Secondary object

equals

public boolean equals(Object object)

Compares this Pair to the specified object. The result is true if and only if the argument is not null and is a Pair object whose primary and secondary objects are the same as those of this object. For comparing corresponding primary and secondary objects of the 2 instances, the equals() method of those objects will be invoked.

Overrides:

equals in class Object

Parameters:

object - Object to compare this instance to.

Returns:

true if the objects are equal, false otherwise.

compareTo

public int compareTo(Object another)

Compares this object with the specified object for order. Returns a negative integer, zero or a positive integer as this object is less than, equal to or greater than the specified object.

First invokes the compareTo() method on the primary member of this object to compare it with the primary member of the passed object. If the result is non-zero, it returns with this result. If the result is zero, it then invokes the same method on the secondary member of this object to compare that with the secondary member of the passed object. Returns the result of this second comparison.

In essence, the ordering is based on the primary object. The primary object being the same, the ordering is then based on the secondary object. A null primary/secondary object is assumed to be less than a non-null primary/secondary object.

Note: If you will be using instances of this class in collection classes, then you must make sure that both primary and secondary objects are instances of classes that implement the Comparable interface. You must also make sure that all Pair instances in the collection have primary objects of the same type and secondary objects of the same type.

Specified by:

compareTo in interface Comparable

Parameters:

another - Object to compare this instance to.

Returns:

A negative integer, zero or a positive integer as this object is less than, equal to or greater than the specified object.

Throws:

NullPointerException - If the passed object is null

ClassCastException - If the specified object's type prevents it from being compared to this instance or if at least one of the primary and secondary objects of the two compared Pair instances does not implement the Comparable interface.

See Also:

Comparable.compareTo(Object)

hashCode

public int hashCode()

Returns a hash code value for the object. This hash code is computed as the average hash code of the primary and secondary objects. Though this is not a very efficient method, it does rely on the hashCode method implementation of the contained objects.

Overrides:

hashCode in class Object

Returns:

Hash code value for the object.

toString

public String toString()

Returns a string form of the primary and secondary objects. Invokes the toString() method of each object.

Overrides:

toString in class Object

Returns:

String containing the values of primary and secondary objects