/*license*\
XBN-Java: Copyright (C) 2014, Jeff Epstein (aliteralmind __DASH__ github __AT__ yahoo __DOT__ com)
This software is dual-licensed under the:
- Lesser General Public License (LGPL) version 3.0 or, at your option, any later version;
- Apache Software License (ASL) version 2.0.
Either license may be applied at your discretion. More information may be found at
- http://en.wikipedia.org/wiki/Multi-licensing.
The text of both licenses is available in the root directory of this project, under the names "LICENSE_lgpl-3.0.txt" and "LICENSE_asl-2.0.txt". The latest copies may be downloaded at:
- LGPL 3.0: https://www.gnu.org/licenses/lgpl-3.0.txt
- ASL 2.0: http://www.apache.org/licenses/LICENSE-2.0.txt
\*license*/
package com.github.xbn.util;
import java.util.Objects;
import com.github.xbn.lang.Copyable;
import com.github.xbn.lang.CrashIfObject;
import java.util.Comparator;
/**
<p>{@code Comparator} that uses the {@code Comparable} object itself to do the comparison.</p>
* @since 0.1.0
* @author Copyright (C) 2014, Jeff Epstein ({@code aliteralmind __DASH__ github __AT__ yahoo __DOT__ com}), dual-licensed under the LGPL (version 3.0 or later) or the ASL (version 2.0). See source code for details. <a href="http://xbnjava.aliteralmind.com">{@code http://xbnjava.aliteralmind.com}</a>, <a href="https://github.com/aliteralmind/xbnjava">{@code https://github.com/aliteralmind/xbnjava}</a>
**/
public class SelfComparator<M extends Comparable<? super M>> implements Comparator<M>, Copyable {
private boolean bAsc = false;
public SelfComparator() {
}
/**
<p>Create a new {@code SelfComparator}.</p>
* @param is_ascending If {@code true}, then the comparator requires ascending order. If {@code false}, descending (see {@link #compare(M, M) compare(M,M)}). Get with {@link #isAscending() isAscending}{@code ()}.
* @see #SelfComparator(SelfComparator) this(sc)
*/
public SelfComparator(boolean is_ascending) {
bAsc = is_ascending;
}
/**
<p>Create a new {@code SelfComparator}, as a duplicate of another.</p>
<p>This<ol>
<li>Sets {@link #isAscending() isAscending}{@code ()} to {@code to_copy.isAscending()}</li>
</ol></p>
* @see #SelfComparator(boolean) this(b)
*/
public SelfComparator(SelfComparator<M> to_copy) {
try {
bAsc = to_copy.isAscending();
} catch(RuntimeException rx) {
throw CrashIfObject.nullOrReturnCause(to_copy, "to_copy", null, rx);
}
}
/**
* @param o_1 May not be {@code null}.
* @param o_2 May not be {@code null}
* @return If {@link #isAscending() isAscending}{@code ()} is<ul>
<li>{@code true}: {@code o_1.compareTo(o_2)}</li>
<li>{@code false}: {@code (o_1.compareTo(o_2) * -1)}</li>
</ul>
*/
public int compare(M o_1, M o_2) {
int icmpr = -1;
try {
icmpr = o_1.compareTo(o_2);
} catch(RuntimeException rx) {
Objects.requireNonNull(o_1, "o_1");
throw CrashIfObject.nullOrReturnCause(o_2, "o_2", null, rx);
}
if(!isAscending()) {
return (icmpr * -1);
}
return icmpr;
}
@Override public int hashCode() {
return 27;
}
/**
* @param to_compareTo May not be {@code null}.
*/
@Override public boolean equals(Object to_compareTo) {
if(to_compareTo == null) {
throw new NullPointerException("to_compareTo");
}
if(this == to_compareTo) {
return true;
}
/**
http://www.javapractices.com/topic/TopicAction.do?Id=17
downloaded 10/14/2010
use instanceof instead of getClass here for two reasons
1. if need be, it can match any supertype, and not just one class;
2. it renders an explict check for "that == null" redundant, since
it does the check for null already - "null instanceof [type]" always
returns false. (See Effective Java by Joshua Bloch.)
[[[
Item two is wrong. When the parameter is null, it should throw an npx instead of throwing false:
See: xbnjava\z_build\answers\is-it-a-bad-idea-if-equalsnull-throws-nullpointerexception-instead.txt
]]]
*/
if(!(to_compareTo instanceof SelfComparator)) {
return false;
}
//Safe to cast
@SuppressWarnings("unchecked") //instanceof does not recognize generics
SelfComparator<M> selfCmpr = (SelfComparator<M>)to_compareTo;
//Field-by-field comparison
return isAscending() == selfCmpr.isAscending();
}
/**
<p>Should the comparison be ordered ascending?.</p>
* @see #SelfComparator(boolean) this(b)
*/
public final boolean isAscending() {
return bAsc;
}
/**
<p>Duplicate this {@code SelfComparator}.</p>
* @return <code>(new {@link #SelfComparator(SelfComparator) SelfComparator}<M>(this))</code>
*/
public SelfComparator<M> getObjectCopy() {
return (new SelfComparator<M>(this));
}
}