java.util

Interface Comparator<T>

All Known Implementing Classes:

CaseInsensitiveOrder

public interface Comparator<T>

A Comparator is used to compare two objects to determine their ordering with respect to each other. On a given Collection, a Comparator can be used to obtain a sorted Collection which is totally ordered. For a Comparator to be consistent with equals, its {code #compare(Object, Object)} method has to return zero for each pair of elements (a,b) where a.equals(b) holds true. It is recommended that a Comparator implements Serializable.

Since:

1.2

Method Summary

Modifier and Type	Method and Description
int	compare(T object1, T object2) Compares the two specified objects to determine their relative ordering.
boolean	equals(Object object) Compares this Comparator with the specified Object and indicates whether they are equal.

Method Detail

compare

int compare(T object1,
            T object2)

Compares the two specified objects to determine their relative ordering. The ordering implied by the return value of this method for all possible pairs of (object1, object2) should form an equivalence relation. This means that

• compare(a,a) returns zero for all a
• the sign of compare(a,b) must be the opposite of the sign of compare(b,a) for all pairs of (a,b)
• From compare(a,b) > 0 and compare(b,c) > 0 it must follow compare(a,c) > 0 for all possible combinations of (a,b,c)

Parameters:

object1 - an Object.

object2 - a second Object to compare with object1.

Returns:

an integer < 0 if object1 is less than object2, 0 if they are equal, and > 0 if object1 is greater than object2.

Throws:

ClassCastException - if objects are not of the correct type.

equals

boolean equals(Object object)

Compares this Comparator with the specified Object and indicates whether they are equal. In order to be equal, object must represent the same object as this instance using a class-specific comparison.

A Comparator never needs to override this method, but may choose so for performance reasons.

Overrides:

equals in class Object

Parameters:

object - the Object to compare with this comparator.

Returns:

boolean true if specified Object is the same as this Object, and false otherwise.

See Also:

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