Class Constant<T>

java.lang.Object
org.apache.commons.functor.core.Constant<T>
Type Parameters:
T - the returned value type.
All Implemented Interfaces:
Serializable, BinaryFunction<Object,Object,T>, BinaryFunctor<Object,Object>, BinaryPredicate<Object,Object>, Function<T>, Functor, NullaryFunctor, Predicate, UnaryFunction<Object,T>, UnaryFunctor<Object>, UnaryPredicate<Object>
public final class Constant<T> extends Object implements Function<T>, UnaryFunction<Object,T>, BinaryFunction<Object,Object,T>, Predicate, UnaryPredicate<Object>, BinaryPredicate<Object,Object>, Serializable
Evaluates to constant value.

Tests to a constant value, assuming a boolean of Boolean value is supplied. Note that although this class implements Serializable, a given instance will only be truly Serializable if the constant Object is. Attempts to serialize an instance whose value is not Serializable will result in an exception.

Version:
$Revision$ $Date$
See Also:

  • Field Details

    • TRUE

      public static final Constant<Boolean> TRUE
      Constant for true.

    • FALSE

      public static final Constant<Boolean> FALSE
      Constant for false.

    • serialVersionUID

      private static final long serialVersionUID
      serialVersionUID declaration.
      See Also:

    • value

      private final T value
      The constant value.

  • Constructor Details

    • Constant

      public Constant(T value)
      Create a new Constant.
      Parameters:
      value - Object

  • Method Details

    • evaluate

      public T evaluate()
      Evaluate this function.
      Specified by:
      evaluate in interface Function<T>
      Returns:
      the T result of this evaluation

    • evaluate

      public T evaluate(Object obj)
      Evaluate this function.
      Specified by:
      evaluate in interface UnaryFunction<Object,T>
      Parameters:
      obj - the A object to evaluate
      Returns:
      the T result of this evaluation

    • evaluate

      public T evaluate(Object left, Object right)
      Evaluate this function.
      Specified by:
      evaluate in interface BinaryFunction<Object,Object,T>
      Parameters:
      left - the L element of the ordered pair of arguments
      right - the R element of the ordered pair of arguments
      Returns:
      the T result of this function for the given arguments

    • test

      public boolean test()
      Evaluate this predicate.
      Specified by:
      test in interface Predicate
      Returns:
      the result of this test

    • test

      public boolean test(Object obj)
      Evaluate this predicate.
      Specified by:
      test in interface UnaryPredicate<T>
      Parameters:
      obj - the A object to test
      Returns:
      the result of this test

    • test

      public boolean test(Object left, Object right)
      Evaluate this predicate.
      Specified by:
      test in interface BinaryPredicate<Object,Object>
      Parameters:
      left - the L element of the ordered pair of arguments
      right - the R element of the ordered pair of arguments
      Returns:
      the result of this test for the given arguments

    • equals

      public boolean equals(Object that)
      Indicates whether some other object is "equal to" this functor. This method must adhere to general Object.equals contract. Additionally, this method can return true only if the specified Object implements the same functor interface and is known to produce the same results and/or side-effects for the same arguments (if any).

      While implementators are strongly encouraged to override the default Object implementation of this method, note that the default Object implementation does in fact adhere to the functor equals contract.

      Specified by:
      equals in interface Functor
      Overrides:
      equals in class Object
      Parameters:
      that - the object to compare this functor to
      Returns:
      true iff the given object implements this functor interface, and is known to produce the same results and/or side-effects for the same arguments (if any).
      See Also:

    • equals

      public boolean equals(Constant<?> that)
      Learn whether another Constant is equal to this.
      Parameters:
      that - Constant to test
      Returns:
      boolean

    • hashCode

      public int hashCode()
      Returns a hash code for this functor adhering to the general Object.hashCode contract. Implementators are strongly encouraged but not strictly required to override the default Object implementation of this method.
      Specified by:
      hashCode in interface Functor
      Overrides:
      hashCode in class Object
      Returns:
      a hash code for this functor
      See Also:

    • toString

      public String toString()
      Returns a human readable description of this functor. Implementators are strongly encouraged but not strictly required to override the default Object implementation of this method.
      Specified by:
      toString in interface Functor
      Overrides:
      toString in class Object
      Returns:
      a human readable description of this functor

    • truePredicate

      public static Constant<Boolean> truePredicate()
      Get a Constant that always returns true.
      Returns:
      a Constant that always returns true

    • falsePredicate

      public static Constant<Boolean> falsePredicate()
      Get a Constant that always returns false.
      Returns:
      a Constant that always returns false

    • predicate

      public static Constant<Boolean> predicate(boolean value)
      Get a Constant that always returns value.
      Parameters:
      value - the constant value
      Returns:
      a Constant that always returns value

    • of

      public static <T> Constant<T> of(T value)
      Get a Constant instance for the specified value.
      Type Parameters:
      T - the constant value
      Parameters:
      value - T
      Returns:
      Constant