Package org.apache.commons.collections4.functors

Class ConstantTransformer<I,​O>

  • All Implemented Interfaces:
    java.io.Serializable, Transformer<I,​O>
    public class ConstantTransformer<I,​O>
extends java.lang.Object
implements Transformer<I,​O>, 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

    • Field Detail

      • NULL_INSTANCE

        public static final Transformer NULL_INSTANCE
        Returns null each time

    • Constructor Detail

      • ConstantTransformer

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

    • Method Detail

      • nullTransformer

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

      • 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.

      • transform

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

      • getConstant

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

      • equals

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

      • hashCode

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