org.moeaframework.core.variable
Class Permutation

java.lang.Object
  org.moeaframework.core.variable.Permutation

All Implemented Interfaces:

Serializable, Variable

public class Permutation
extends Object
implements Variable

Decision variable for permutations.

See Also:

Serialized Form

Constructor Summary

Permutation(int size)
Constructs a permutation variable with the specified number of elements.

Permutation(int[] permutation)
Constructs a permutation variable using the specified permutation array.

Method Summary

Permutation	copy() Returns an independent copy of this decision variable.
boolean	equals(Object obj) Indicates whether some other object is "equal to" this one.
void	fromArray(int[] permutation) Sets the permutation array.
int	get(int index) Returns the value of the permutation at the specified index.
int	hashCode() Returns a hash code value for the object.
void	insert(int i, int j) Removes the ith element and inserts it at the jth position.
static boolean	isPermutation(int[] permutation) Returns true if the specified permutation is valid; false otherwise.
int	size() Returns the number of elements in this permutation.
void	swap(int i, int j) Swaps the ith and jth elements in this permutation.
int[]	toArray() Returns a copy of the permutation array.

Methods inherited from class java.lang.Object

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

Constructor Detail

Permutation

public Permutation(int size)

Constructs a permutation variable with the specified number of elements.

Parameters:

size - the number of elements in the permutation

Permutation

public Permutation(int[] permutation)

Constructs a permutation variable using the specified permutation array.

Parameters:

permutation - the permutation array

Throws:

IllegalArgumentException - if the permutation array is not a valid permutation

Method Detail

copy

public Permutation copy()

Description copied from interface: Variable

Returns an independent copy of this decision variable. It is required that x.copy() is completely independent from x. This means any method invoked on x.copy() in no way alters the state of x and vice versa. It is typically the case that x.copy().getClass() == x.getClass() and x.copy().equals(x).

Specified by:

copy in interface Variable

Returns:

an independent copy of this decision variable

size

public int size()

Returns the number of elements in this permutation.

Returns:

the number of elements in this permutation

get

public int get(int index)

Returns the value of the permutation at the specified index.

Parameters:

index - the index of the permutation value to be returned

Returns:

the permutation element at the specified index

Throws:

ArrayOutOfBoundsException - if the index is out of range [0, size()-1]

swap

public void swap(int i,
                 int j)

Swaps the ith and jth elements in this permutation.

Parameters:

i - the first index

j - the second index

Throws:

ArrayIndexOutOfBoundsException - if i or j is out or range @{code [0, size()-1]}

insert

public void insert(int i,
                   int j)

Removes the ith element and inserts it at the jth position.

Parameters:

i - the first index

j - the second index

Throws:

ArrayIndexOutOfBoundsException - if i or j is out or range @{code [0, size()-1]}

toArray

public int[] toArray()

Returns a copy of the permutation array.

Returns:

a copy of the permutation array

fromArray

public void fromArray(int[] permutation)

Sets the permutation array.

Parameters:

permutation - the permutation array

Throws:

IllegalArgumentException - if the permutation array is not a valid permutation

isPermutation

public static boolean isPermutation(int[] permutation)

Returns true if the specified permutation is valid; false otherwise.

Parameters:

permutation - the permutation array

Returns:

true if the specified permutation is valid; false otherwise

hashCode

public int hashCode()

Description copied from class: java.lang.Object

Returns a hash code value for the object. This method is supported for the benefit of hashtables such as those provided by java.util.Hashtable.

The general contract of hashCode is:

• Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer, provided no information used in equals comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application.
• If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result.
• It is not required that if two objects are unequal according to the Object.equals(java.lang.Object) method, then calling the hashCode method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hashtables.

As much as is reasonably practical, the hashCode method defined by class Object does return distinct integers for distinct objects. (This is typically implemented by converting the internal address of the object into an integer, but this implementation technique is not required by the Java^TM programming language.)

Overrides:

hashCode in class Object

Returns:

a hash code value for this object.

See Also:

Object.equals(java.lang.Object), Hashtable

equals

public boolean equals(Object obj)

Description copied from class: java.lang.Object

Indicates whether some other object is "equal to" this one.

The equals method implements an equivalence relation on non-null object references:

• It is reflexive: for any non-null reference value x, x.equals(x) should return true.
• It is symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true.
• It is transitive: for any non-null reference values x, y, and z, if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true.
• It is consistent: for any non-null reference values x and y, multiple invocations of x.equals(y) consistently return true or consistently return false, provided no information used in equals comparisons on the objects is modified.
• For any non-null reference value x, x.equals(null) should return false.

The equals method for class Object implements the most discriminating possible equivalence relation on objects; that is, for any non-null reference values x and y, this method returns true if and only if x and y refer to the same object (x == y has the value true).

Note that it is generally necessary to override the hashCode method whenever this method is overridden, so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes.

Overrides:

equals in class Object

Parameters:

obj - the reference object with which to compare.

Returns:

true if this object is the same as the obj argument; false otherwise.

See Also:

Object.hashCode(), Hashtable