Package org.apache.commons.collections4.functors

Class ConstantTransformer<I,O>

java.lang.Object

org.apache.commons.collections4.functors.ConstantTransformer<I,O>

All Implemented Interfaces:

Serializable, Function<I,O>, Transformer<I,O>

public class ConstantTransformer<I,O>
extends Object
implements Transformer<I,O>, 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 Summary

Fields

Modifier and Type	Field	Description
static final Transformer	NULL_INSTANCE	Returns null each time

Constructor Summary

Constructors

Constructor	Description
ConstantTransformer(O constantToReturn)	Constructor that performs no validation.

Method Summary

Modifier and Type	Method	Description
static <I, O> Transformer<I,O>	constantTransformer(O constantToReturn)	Transformer method that performs validation.
boolean	equals(Object obj)
O	getConstant()	Gets the constant.
int	hashCode()
static <I, O> Transformer<I,O>	nullTransformer()	Gets a typed null instance.
O	transform(I 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

Field Details

NULL_INSTANCE

public static final Transformer NULL_INSTANCE

Returns null each time

Constructor Details

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 Details

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(Object obj)

Overrides:

equals in class Object

getConstant

public O getConstant()

Gets the constant.

Returns:

the constant

Since:

3.1

hashCode

public int hashCode()

Overrides:

hashCode in class Object

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