org.aspectj.util.PartialOrder Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of aspectjweaver Show documentation
Show all versions of aspectjweaver Show documentation
The AspectJ weaver applies aspects to Java classes. It can be used as a Java agent in order to apply load-time
weaving (LTW) during class-loading and also contains the AspectJ runtime classes.
/* *******************************************************************
* Copyright (c) 1999-2001 Xerox Corporation,
* 2002 Palo Alto Research Center, Incorporated (PARC).
* All rights reserved.
* This program and the accompanying materials are made available
* under the terms of the Eclipse Public License v 2.0
* which accompanies this distribution and is available at
* https://www.eclipse.org/org/documents/epl-2.0/EPL-2.0.txt
*
* Contributors:
* Xerox/PARC initial implementation
* ******************************************************************/
package org.aspectj.util;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
/**
* This class implements a partial order
*
* It includes routines for doing a topo-sort
*/
public class PartialOrder {
/**
* All classes that want to be part of a partial order must implement PartialOrder.PartialComparable.
*/
public interface PartialComparable {
/**
* @return
* - +1 if this is greater than other
* - -1 if this is less than other
* - 0 if this is not comparable to other
*
*
* Note: returning 0 from this method doesn't mean the same thing as returning 0 from
* java.util.Comparable.compareTo()
*/
int compareTo(Object other);
/**
* This method can provide a deterministic ordering for elements that are strictly not comparable. If you have no need for
* this, this method can just return 0 whenever called.
*/
int fallbackCompareTo(Object other);
}
private static class SortObject {
T object;
List> smallerObjects = new LinkedList<>();
List> biggerObjects = new LinkedList<>();
public SortObject(T o) {
object = o;
}
boolean hasNoSmallerObjects() {
return smallerObjects.size() == 0;
}
boolean removeSmallerObject(SortObject o) {
smallerObjects.remove(o);
return hasNoSmallerObjects();
}
void addDirectedLinks(SortObject other) {
int cmp = object.compareTo(other.object);
if (cmp == 0) {
return;
}
if (cmp > 0) {
this.smallerObjects.add(other);
other.biggerObjects.add(this);
} else {
this.biggerObjects.add(other);
other.smallerObjects.add(this);
}
}
public String toString() {
return object.toString(); // +smallerObjects+biggerObjects;
}
}
private static void addNewPartialComparable(List> graph, T o) {
SortObject so = new SortObject<>(o);
for (SortObject other : graph) {
so.addDirectedLinks(other);
}
graph.add(so);
}
private static void removeFromGraph(List> graph, SortObject o) {
for (Iterator> i = graph.iterator(); i.hasNext();) {
SortObject other = i.next();
if (o == other) {
i.remove();
}
// ??? could use this to build up a new queue of objects with no
// ??? smaller ones
other.removeSmallerObject(o);
}
}
/**
* @param objects must all implement PartialComparable
*
* @return the same members as objects, but sorted according to their partial order. returns null if the objects are cyclical
*
*/
public static List sort(List objects) {
// lists of size 0 or 1 don't need any sorting
if (objects.size() < 2) {
return objects;
}
// ??? we might want to optimize a few other cases of small size
// ??? I don't like creating this data structure, but it does give good
// ??? separation of concerns.
List> sortList = new LinkedList<>();
for (T object : objects) {
addNewPartialComparable(sortList, object);
}
// System.out.println(sortList);
// now we have built our directed graph
// use a simple sort algorithm from here
// can increase efficiency later
// List ret = new ArrayList(objects.size());
final int N = objects.size();
for (int index = 0; index < N; index++) {
// System.out.println(sortList);
// System.out.println("-->" + ret);
SortObject leastWithNoSmallers = null;
for (SortObject so: sortList) {
if (so.hasNoSmallerObjects()) {
if (leastWithNoSmallers == null || so.object.fallbackCompareTo(leastWithNoSmallers.object) < 0) {
leastWithNoSmallers = so;
}
}
}
if (leastWithNoSmallers == null) {
return null;
}
removeFromGraph(sortList, leastWithNoSmallers);
objects.set(index, leastWithNoSmallers.object);
}
return objects;
}
/***********************************************************************************
* /* a minimal testing harness
***********************************************************************************/
static class Token implements PartialComparable {
private String s;
Token(String s) {
this.s = s;
}
public int compareTo(Object other) {
Token t = (Token) other;
int cmp = s.charAt(0) - t.s.charAt(0);
if (cmp == 1) {
return 1;
}
if (cmp == -1) {
return -1;
}
return 0;
}
public int fallbackCompareTo(Object other) {
return -s.compareTo(((Token) other).s);
}
public String toString() {
return s;
}
}
public static void main(String[] args) {
List l = new ArrayList<>();
l.add(new Token("a1"));
l.add(new Token("c2"));
l.add(new Token("b3"));
l.add(new Token("f4"));
l.add(new Token("e5"));
l.add(new Token("d6"));
l.add(new Token("c7"));
l.add(new Token("b8"));
l.add(new Token("z"));
l.add(new Token("x"));
l.add(new Token("f9"));
l.add(new Token("e10"));
l.add(new Token("a11"));
l.add(new Token("d12"));
l.add(new Token("b13"));
l.add(new Token("c14"));
System.out.println(l);
sort(l);
System.out.println(l);
}
}