java.util
Interface Comparator

All Known Implementing Classes:

java.lang.String.CaseInsensitiveComparator, CompareTabOrderComparator, sun.awt.datatransfer.DataTransferer.IndexedComparator, LayoutComparator, java.util.Collections.ReverseComparator

public interface Comparator

Untamed:

Method Summary

int	compare(Object o1, Object o2) Enabled: Compares its two arguments for order.
boolean	equals(Object obj) Suppressed: Indicates whether some other object is "equal to" this Comparator.

Method Detail

compare

public int compare(Object o1,
                   Object o2)

Enabled: Compares its two arguments for order. Returns a negative integer, zero, or a positive integer as the first argument is less than, equal to, or greater than the second.

The implementor must ensure that sgn(compare(x, y)) == -sgn(compare(y, x)) for all x and y. (This implies that compare(x, y) must throw an exception if and only if compare(y, x) throws an exception.)

The implementor must also ensure that the relation is transitive: ((compare(x, y)>0) && (compare(y, z)>0)) implies compare(x, z)>0.

Finally, the implementer must ensure that compare(x, y)==0 implies that sgn(compare(x, z))==sgn(compare(y, z)) for all z.

It is generally the case, but not strictly required that (compare(x, y)==0) == (x.equals(y)). Generally speaking, any comparator that violates this condition should clearly indicate this fact. The recommended language is "Note: this comparator imposes orderings that are inconsistent with equals."

Parameters:

o1 - the first object to be compared.

o2 - the second object to be compared.

Returns:

a negative integer, zero, or a positive integer as the first argument is less than, equal to, or greater than the second.

Throws:

ClassCastException - if the arguments' types prevent them from being compared by this Comparator.

equals

public boolean equals(Object obj)

Suppressed: Indicates whether some other object is "equal to" this Comparator. This method must obey the general contract of Object.equals(Object). Additionally, this method can return true only if the specified Object is also a comparator and it imposes the same ordering as this comparator. Thus, comp1.equals(comp2) implies that sgn(comp1.compare(o1, o2))==sgn(comp2.compare(o1, o2)) for every object reference o1 and o2.

Note that it is always safe not to override Object.equals(Object). However, overriding this method may, in some cases, improve performance by allowing programs to determine that two distinct Comparators impose the same order.

Overrides:

equals in class Object

Parameters:

obj - the reference object with which to compare.

Returns:

true only if the specified object is also a comparator and it imposes the same ordering as this comparator.

See Also:

java.lang.Object#equals(java.lang.Object), java.lang.Object#hashCode()