org.hsqldb.lib.ObjectComparator Maven / Gradle / Ivy
/* Copyright (c) 2001-2021, The HSQL Development Group
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* Neither the name of the HSQL Development Group nor the names of its
* contributors may be used to endorse or promote products derived from this
* software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL HSQL DEVELOPMENT GROUP, HSQLDB.ORG,
* OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package org.hsqldb.lib;
/**
* Interface for equality comparison.
*
* The equals and hashCode methods of this interace are used instead of
* the methods of the compared Objects.
*
* The DefaultComparator implmentation calls the Object's methods.
*
* The IdentityComparator implementation uses {@code ==} instead of the equals
* method of the Object.
*
* Updated for generics fredt@users.
*
* @author fredt@users
* @version 2.6.0
* @since 2.0
*/
public interface ObjectComparator {
boolean equals(T a, T b);
int hashCode(T a);
long longKey(T a);
ObjectComparator defaultComparator = new DefaultComparator();
ObjectComparator identityComparator = new IdentityComparator();
/**
* Comparator that uses identity for Object equality.
*/
class IdentityComparator implements ObjectComparator {
public boolean equals(Object a, Object b) {
return a == b;
}
public int hashCode(Object a) {
return a == null ? 0 :
a.hashCode();
}
public long longKey(Object a) {
return 0L;
}
}
/**
* Comparator that uses the equals and hash code methods of Objects.
*/
class DefaultComparator implements ObjectComparator {
public boolean equals(Object a, Object b) {
return a == b || (a != null && a.equals(b));
}
public int hashCode(Object a) {
return a == null ? 0 :
a.hashCode();
}
public long longKey(Object a) {
return 0L;
}
}
}