org.apache.commons.collections4.functors

Class ComparatorPredicate<T>

java.lang.Object

org.apache.commons.collections4.functors.ComparatorPredicate<T>

All Implemented Interfaces:

java.io.Serializable, Predicate<T>

public class ComparatorPredicate<T>
extends java.lang.Object
implements Predicate<T>, java.io.Serializable

Predicate that compares the input object with the one stored in the predicate using a comparator. In addition, the comparator result can be evaluated in accordance to a supplied criterion value.

In order to demonstrate the use of the predicate, the following variables are declared:

 Integer ONE = Integer.valueOf(1);
 Integer TWO = Integer.valueOf(2);

 Comparator comparator = new Comparator() {

     public int compare(Object first, Object second) {
         return ((Integer) second) - ((Integer) first);
     }

 };
 

Using the declared variables, the ComparatorPredicate can be used used in the following way:

 ComparatorPredicate.comparatorPredicate(ONE, comparator).evaluate(TWO);
 

The input variable TWO in compared to the stored variable ONE using the supplied comparator. This is the default usage of the predicate and will return true if the underlying comparator returns 0. In addition to the default usage of the predicate, it is possible to evaluate the comparator's result in several ways. The following ComparatorPredicate.Criterion enumeration values are provided by the predicate:

• EQUAL
• GREATER
• GREATER_OR_EQUAL
• LESS
• LESS_OR_EQUAL

The following examples demonstrates how these constants can be used in order to manipulate the evaluation of a comparator result.

 ComparatorPredicate.comparatorPredicate(ONE, comparator,ComparatorPredicate.Criterion.GREATER).evaluate(TWO);
 

The input variable TWO is compared to the stored variable ONE using the supplied comparator using the GREATER evaluation criterion constant. This instructs the predicate to return true if the comparator returns a value greater than 0.

Since:

4.0

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ComparatorPredicate.Criterion

Constructor Summary

Constructors

Constructor and Description
ComparatorPredicate(T object, java.util.Comparator<T> comparator, ComparatorPredicate.Criterion criterion) Constructor that performs no validation.

Method Summary

Modifier and Type	Method and Description
static <T> Predicate<T>	comparatorPredicate(T object, java.util.Comparator<T> comparator) Factory to create the comparator predicate
static <T> Predicate<T>	comparatorPredicate(T object, java.util.Comparator<T> comparator, ComparatorPredicate.Criterion criterion) Factory to create the comparator predicate
boolean	evaluate(T target) Evaluates the predicate.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ComparatorPredicate

public ComparatorPredicate(T object,
                           java.util.Comparator<T> comparator,
                           ComparatorPredicate.Criterion criterion)

Constructor that performs no validation. Use comparatorPredicate if you want that.

Parameters:

object - the object to compare to

comparator - the comparator to use for comparison

criterion - the criterion to use to evaluate comparison

Method Detail

comparatorPredicate

public static <T> Predicate<T> comparatorPredicate(T object,
                                                   java.util.Comparator<T> comparator)

Factory to create the comparator predicate

Type Parameters:

T - the type that the predicate queries

Parameters:

object - the object to compare to

comparator - the comparator to use for comparison

Returns:

the predicate

Throws:

java.lang.NullPointerException - if comparator is null

comparatorPredicate

public static <T> Predicate<T> comparatorPredicate(T object,
                                                   java.util.Comparator<T> comparator,
                                                   ComparatorPredicate.Criterion criterion)

Factory to create the comparator predicate

Type Parameters:

T - the type that the predicate queries

Parameters:

object - the object to compare to

comparator - the comparator to use for comparison

criterion - the criterion to use to evaluate comparison

Returns:

the predicate

Throws:

java.lang.NullPointerException - if comparator or criterion is null

evaluate

public boolean evaluate(T target)

Evaluates the predicate. The predicate evaluates to true in the following cases:

• comparator.compare(object, input) == 0 && criterion == EQUAL
• comparator.compare(object, input) < 0 && criterion == LESS
• comparator.compare(object, input) > 0 && criterion == GREATER
• comparator.compare(object, input) >= 0 && criterion == GREATER_OR_EQUAL
• comparator.compare(object, input) <= 0 && criterion == LESS_OR_EQUAL

Specified by:

evaluate in interface Predicate<T>

Parameters:

target - the target object to compare to

Returns:

true if the comparison succeeds according to the selected criterion

Throws:

java.lang.IllegalStateException - if the criterion is invalid (really not possible)

See Also:

Predicate.evaluate(java.lang.Object), Comparator.compare(java.lang.Object first, java.lang.Object second)