util

Class Pair<C1,C2>

java.lang.Object

util.Pair<C1,C2>

All Implemented Interfaces:

java.lang.Comparable<Pair<C1,C2>>

public class Pair<C1,C2>
extends java.lang.Object
implements java.lang.Comparable<Pair<C1,C2>>

A simple class to manipulate a pair of elements. Note that a pair is not immutable and may not be safe in a set or a map.

Constructor Summary

Constructors

Constructor and Description
Pair(C1 e1, C2 e2) Creates a pair from the two specified elements.

Method Summary

Methods

Modifier and Type	Method and Description
static <O> java.lang.Iterable<Pair<O,O>>	allPairs(java.util.List<? extends O> l) Returns the list of pairs of elements in the specified list, excluding the identical pairs and the reversed pairs.
int	compareTo(Pair<C1,C2> pair) Compares this pair to the specified object.
boolean	equals(java.lang.Object o) Indicates whether the specified object equals this pair.
C1	first() Access to the first element of this pair.
int	hashCode() Returns a hashcode for this pair.
static int	hashCode(java.lang.Object e1, java.lang.Object e2) Returns the hash code value of the specified pair of elements.
static <C1,C2> Pair<C1,C2>	newPair(C1 e1, C2 e2) Static constructor.
C2	second() Access to the second element of this pair.
void	setFirst(C1 e) Changes the first element of the pair.
void	setSecond(C2 e) Changes the second element of the pair.
java.lang.String	toString() Returns a string representation of this pair.

Methods inherited from class java.lang.Object

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

Constructor Detail

Pair

public Pair(C1 e1,
    C2 e2)

Creates a pair from the two specified elements.

Parameters:

e1 - the first element.

e2 - the second element.

Method Detail

newPair

public static <C1,C2> Pair<C1,C2> newPair(C1 e1,
                          C2 e2)

Static constructor.

Type Parameters:

C1 - the type of the first element.

C2 - the type of the second element.

Parameters:

e1 - the first element of the pair.

e2 - the second element of the pair.

hashCode

public int hashCode()

Returns a hashcode for this pair. This method calls the hashcode() method of each object each time it is called.

Overrides:

hashCode in class java.lang.Object

Returns:

a hashcode value for this pair.

equals

public boolean equals(java.lang.Object o)

Indicates whether the specified object equals this pair. To equal this pair, the object must be a pair such that its elements equal the elements of this pair.

Overrides:

equals in class java.lang.Object

Parameters:

o - the object to compare to this pair.

Returns:

true if o equals this.

compareTo

public int compareTo(Pair<C1,C2> pair)

Compares this pair to the specified object. The result is the comparison of the first elements of both pairs or, if the first elements are equal, the second elements.

Specified by:

compareTo in interface java.lang.Comparable<Pair<C1,C2>>

Parameters:

pair - the object to compare to this.

Returns:

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

Throws:

java.lang.ClassCastException - if o is not a pair, or if the objects of the pair cannot be compared, or if their comparison throws an exception.

first

public C1 first()

Access to the first element of this pair.

Returns:

the first element of this pair.

second

public C2 second()

Access to the second element of this pair.

Returns:

the second element of this pair.

setFirst

public void setFirst(C1 e)

Changes the first element of the pair.

Parameters:

e - the new first element.

setSecond

public void setSecond(C2 e)

Changes the second element of the pair.

Parameters:

e - the new second element.

toString

public java.lang.String toString()

Returns a string representation of this pair. The pair is represented by <e1,e2> where e1 and e2 are the string representations of the first and the second element respectively.

Overrides:

toString in class java.lang.Object

Returns:

a string representation of this pair.

hashCode

public static int hashCode(java.lang.Object e1,
           java.lang.Object e2)

Returns the hash code value of the specified pair of elements.

Parameters:

p - the pair.

Returns:

a hash code value of p.

See Also:

hashCode()

allPairs

public static <O> java.lang.Iterable<Pair<O,O>> allPairs(java.util.List<? extends O> l)

Returns the list of pairs of elements in the specified list, excluding the identical pairs and the reversed pairs. So, if the list contains four elements [a,b,c,d], the method returns [[a,b],[a,c],[a,d],[b,c],[b,d],[c,d]].

Parameters:

l - a list of objects.

Returns:

all the pairs in l.