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public interface Comparator<T>
Interface for objects that specify an ordering between objects. The ordering
should be total, such that any two objects of the correct type
can be compared, and the comparison is reflexive, anti-symmetric, and
transitive. It is also recommended that the comparator be consistent
with equals, although this is not a strict requirement. A relation
is consistent with equals if these two statements always have the same
results (if no exceptions occur):
compare((Object) e1, (Object) e2) == 0
and
e1.equals((Object) e2)
Comparators that violate consistency with equals may cause strange behavior
in sorted lists and sets. For example, a case-sensitive dictionary order
comparison of Strings is consistent with equals, but if it is
case-insensitive it is not, because "abc" and "ABC" compare as equal even
though "abc".equals("ABC") returns false.
In general, Comparators should be Serializable, because when they are passed to Serializable data structures such as SortedMap or SortedSet, the entire data structure will only serialize correctly if the comparator is Serializable.
Comparable
,
TreeMap
,
TreeSet
,
SortedMap
,
SortedSet
,
Arrays.sort(Object[], Comparator)
,
Serializable
Method Summary | |
---|---|
int |
compare(T o1,
T o2)
Return an integer that is negative, zero or positive depending on whether the first argument is less than, equal to or greater than the second according to this ordering. |
boolean |
equals(Object obj)
Return true if the object is equal to this object. |
Method Detail |
---|
int compare(T o1, T o2)
Although it is permissible for a comparator to provide an order inconsistent with equals, that should be documented.
o1
- the first objecto2
- the second object
ClassCastException
- if the elements are not of types that can be
compared by this ordering.boolean equals(Object obj)
Object.equals()
, be a Comparator, and impose the
same ordering as this Comparator. The default implementation
inherited from Object is usually adequate.
equals
in class Object
obj
- The object
Object.equals(Object)
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