public interface Comparator<T>

Known subtypesCaseInsensitiveOrder

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 java.io.Serializable.

Methods

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

Method details

compare

public abstract 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 T
an Object.
object2 T
a second Object to compare with object1.

Returns

an integer 0 if object1 is greater than object2.

Throws

ClassCastException
if objects are not of the correct type.

equals

public abstract 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.

Parameters

object 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