org.apache.commons.collections4.functors

Class ComparatorPredicate<T>

  • All Implemented Interfaces:
    Serializable, Predicate<T> 

    public class ComparatorPredicate<T>
extends Object
implements Predicate<T>, 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

    • Constructor Detail

      • ComparatorPredicate

        public ComparatorPredicate(T object,
                           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,
                                                   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:
        NullPointerException - if comparator is null

      • comparatorPredicate

        public static <T> Predicate<T> comparatorPredicate(T object,
                                                   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:
        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:
        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)