ConstantTransformer (Apache Commons Collections 4.0 API)

java.lang.Object
- org.apache.commons.collections4.functors.ConstantTransformer<I,O>

All Implemented Interfaces:

Serializable, 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

Version:

$Id: ConstantTransformer.html 972421 2015-11-14 20:00:04Z tn $

See Also:
Serialized Form

Field Summary

Fields
Modifier and Type Field and Description

static Transformer NULL_INSTANCE
Returns null each time

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

Constructor Summary

Constructors
Constructor and Description

ConstantTransformer(O constantToReturn)
Constructor that performs no validation.

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

Method Summary

Methods
Modifier and Type	Method and 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()` Get 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

- 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 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(Object obj)
```
    Overrides:
    
    equals in class Object
  - hashCode
```
public int hashCode()
```
    Overrides:
    
    hashCode in class Object

Class ConstantTransformer<I,O>

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

NULL_INSTANCE

Constructor Detail

ConstantTransformer

Method Detail

nullTransformer

constantTransformer

transform

getConstant

equals

hashCode