Package org.apache.commons.collections4.functors

Class ConstantTransformer<T,​R>

  • Type Parameters:
    T - the type of the input to the function.
    R - the type of the result of the function.
    All Implemented Interfaces:
    java.io.Serializable, java.util.function.Function<T,​R>, Transformer<T,​R>
    public class ConstantTransformer<T,​R>
extends java.lang.Object
implements Transformer<T,​R>, java.io.Serializable
    Transformer implementation that returns the same constant each time.

    No check is made that the object is immutable. In general, only immutable objects should use the constant factory. Mutable objects should use the prototype factory.

    Since:
    3.0
    See Also:
    Serialized Form

    • Constructor Summary

      Constructors 
      Constructor Description
      ConstantTransformer​(R constantToReturn)
      Constructor that performs no validation.

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      static <I,​O>
      Transformer<I,​O>      		 constantTransformer​(O constantToReturn)
      Transformer method that performs validation.
      boolean equals​(java.lang.Object obj)
      R getConstant()
      Gets the constant.
      int hashCode()
      static <I,​O>
      Transformer<I,​O>      		 nullTransformer()
      Gets a typed null instance.
      R transform​(T input)
      Transforms the input by ignoring it and returning the stored constant instead.

      • Methods inherited from class java.lang.Object

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

      • Methods inherited from interface java.util.function.Function

        andThen, compose

      • Methods inherited from interface org.apache.commons.collections4.Transformer

        apply

    • Constructor Detail

      • ConstantTransformer

        public ConstantTransformer​(R constantToReturn)
        Constructor that performs no validation. Use constantTransformer if you want that.
        Parameters:
        constantToReturn - the constant to return each time

    • Method Detail

      • constantTransformer

        public static <I,​O> Transformer<I,​O> constantTransformer​(O constantToReturn)
        Transformer method that performs validation.
        Type Parameters:
        I - the input type
        O - the output type
        Parameters:
        constantToReturn - the constant object to return each time in the factory
        Returns:
        the constant factory.

      • nullTransformer

        public static <I,​O> Transformer<I,​O> nullTransformer()
        Gets a typed null instance.
        Type Parameters:
        I - the input type
        O - the output type
        Returns:
        Transformer<I, O> that always returns null.

      • equals

        public boolean equals​(java.lang.Object obj)
        Overrides:
        equals in class java.lang.Object

      • getConstant

        public R getConstant()
        Gets the constant.
        Returns:
        the constant
        Since:
        3.1

      • hashCode

        public int hashCode()
        Overrides:
        hashCode in class java.lang.Object

      • transform

        public R transform​(T input)
        Transforms the input by ignoring it and returning the stored constant instead.
        Specified by:
        transform in interface Transformer<T,​R>
        Parameters:
        input - the input object which is ignored
        Returns:
        the stored constant