Package org.apache.commons.collections4.comparators

Class NullComparator<E>

java.lang.Object
org.apache.commons.collections4.comparators.NullComparator<E>
Type Parameters:
E - the type of objects compared by this comparator
All Implemented Interfaces:
Serializable, Comparator<E>
public class NullComparator<E> extends Object implements Comparator<E>, Serializable
A Comparator that will compare nulls to be either lower or higher than other objects.
Since:
2.0
See Also:

  • Constructor Details

    • NullComparator

      public NullComparator()
      Construct an instance that sorts null higher than any non-null object it is compared with. When comparing two non-null objects, the ComparableComparator is used.

    • NullComparator

      public NullComparator(boolean nullsAreHigh)
      Construct an instance that sorts null higher or lower than any non-null object it is compared with. When comparing two non-null objects, the ComparableComparator is used.
      Parameters:
      nullsAreHigh - a true value indicates that null should be compared as higher than a non-null object. A false value indicates that null should be compared as lower than a non-null object.

    • NullComparator

      public NullComparator(Comparator<? super E> nonNullComparator)
      Construct an instance that sorts null higher than any non-null object it is compared with. When comparing two non-null objects, the specified Comparator is used.
      Parameters:
      nonNullComparator - the comparator to use when comparing two non-null objects. This argument cannot be null
      Throws:
      NullPointerException - if nonNullComparator is null

    • NullComparator

      public NullComparator(Comparator<? super E> nonNullComparator, boolean nullsAreHigh)
      Construct an instance that sorts null higher or lower than any non-null object it is compared with. When comparing two non-null objects, the specified Comparator is used.
      Parameters:
      nonNullComparator - the comparator to use when comparing two non-null objects. This argument cannot be null
      nullsAreHigh - a true value indicates that null should be compared as higher than a non-null object. A false value indicates that null should be compared as lower than a non-null object.
      Throws:
      NullPointerException - if nonNullComparator is null

  • Method Details

    • compare

      public int compare(E o1, E o2)
      Perform a comparison between two objects. If both objects are null, a 0 value is returned. If one object is null and the other is not, the result is determined on whether the Comparator was constructed to have nulls as higher or lower than other objects. If neither object is null, an underlying comparator specified in the constructor (or the default) is used to compare the non-null objects.
      Specified by:
      compare in interface Comparator<E>
      Parameters:
      o1 - the first object to compare
      o2 - the object to compare it to.
      Returns:
      -1 if o1 is "lower" than (less than, before, etc.) o2; 1 if o1 is "higher" than (greater than, after, etc.) o2; or 0 if o1 and o2 are equal.

    • equals

      public boolean equals(Object obj)
      Determines whether the specified object represents a comparator that is equal to this comparator.
      Specified by:
      equals in interface Comparator<E>
      Overrides:
      equals in class Object
      Parameters:
      obj - the object to compare this comparator with.
      Returns:
      true if the specified object is a NullComparator with equivalent null comparison behavior (i.e. null high or low) and with equivalent underlying non-null object comparators.

    • hashCode

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