org.apache.commons.collections4.comparators

## Class TransformingComparator<I,O>

- java.lang.Object
- - org.apache.commons.collections4.comparators.TransformingComparator<I,O>

- Type Parameters:
    `I` - the input type to the transformer
    `O` - the output type from the transformer
  All Implemented Interfaces:
    Serializable, Comparator<I>

      public class TransformingComparator<I,O>
      extends Object
      implements Comparator<I>, Serializable

  Decorates another Comparator with transformation behavior. That is, the return value from the transform operation will be passed to the decorated `compare` method.

  This class is Serializable from Commons Collections 4.0.

  Since:
    2.1
  See Also:
    `Transformer`, `ComparableComparator`, Serialized Form

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `TransformingComparator(Transformer<? super I,? extends O> transformer)` Constructs an instance with the given Transformer and a `ComparableComparator`.
    `TransformingComparator(Transformer<? super I,? extends O> transformer, Comparator<O> decorated)` Constructs an instance with the given Transformer and Comparator.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `int` | `compare(I obj1, I obj2)` Returns the result of comparing the values from the transform operation.
    `boolean` | `equals(Object object)` Returns `true` iff that Object is is a `Comparator` whose ordering is known to be equivalent to mine.
    `int` | `hashCode()` Implement a hash code for this comparator that is consistent with `equals`.

    - ### Methods inherited from class java.lang.Object

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

    - ### Methods inherited from interface java.util.Comparator

      `comparing, comparing, comparingDouble, comparingInt, comparingLong, naturalOrder, nullsFirst, nullsLast, reversed, reverseOrder, thenComparing, thenComparing, thenComparing, thenComparingDouble, thenComparingInt, thenComparingLong`

- - ### Constructor Detail

    - #### TransformingComparator

          public TransformingComparator(Transformer<? super I,? extends O> transformer)

      Constructs an instance with the given Transformer and a `ComparableComparator`.
      Parameters:
        `transformer` - what will transform the arguments to `compare`

    - #### TransformingComparator

          public TransformingComparator(Transformer<? super I,? extends O> transformer,
                                        Comparator<O> decorated)

      Constructs an instance with the given Transformer and Comparator.
      Parameters:
        `transformer` - what will transform the arguments to `compare`
        `decorated` - the decorated Comparator

  - ### Method Detail

    - #### compare

          public int compare(I obj1,
                             I obj2)

      Returns the result of comparing the values from the transform operation.
      Specified by:
        `compare` in interface `Comparator<I>`
      Parameters:
        `obj1` - the first object to transform then compare
        `obj2` - the second object to transform then compare
      Returns:
        negative if obj1 is less, positive if greater, zero if equal

    - #### hashCode

          public int hashCode()

      Implement a hash code for this comparator that is consistent with `equals`.
      Overrides:
        `hashCode` in class `Object`
      Returns:
        a hash code for this comparator.

    - #### equals

          public boolean equals(Object object)

      Returns `true` iff that Object is is a `Comparator` whose ordering is known to be equivalent to mine.

      This implementation returns `true` iff `that` is a `TransformingComparator` whose attributes are equal to mine.

      Specified by:
        `equals` in interface `Comparator<I>`
      Overrides:
        `equals` in class `Object`
      Parameters:
        `object` - the object to compare to
      Returns:
        true if equal

Copyright © 2001–2019 The Apache Software Foundation. All rights reserved.