/
Ranking.java
106 lines (99 loc) · 3.34 KB
/
Ranking.java
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package it.polito.utility.stream;
import static java.util.Comparator.comparing;
import static java.util.stream.Collectors.collectingAndThen;
import static java.util.stream.Collectors.groupingBy;
import static java.util.stream.Collectors.joining;
import static java.util.stream.Collectors.toList;
import java.util.Comparator;
import java.util.LinkedList;
import java.util.List;
import java.util.SortedMap;
import java.util.TreeMap;
import java.util.function.Function;
import java.util.stream.Collector;
import java.util.stream.Stream;
/**
*
* @author Marco Torchiano
* @version 1.0
*/
public class Ranking {
/**
*
* @param propertyExtractor
* @param propertyComparator
* @return
*/
static <T,V> Collector<T,?,SortedMap<Integer,List<T>>>
rankingCollector(Function<T,V> propertyExtractor, Comparator<V> propertyComparator){
return collectingAndThen(
groupingBy(propertyExtractor,
()->new TreeMap<>(propertyComparator),
toList()),
map -> map.entrySet().stream().collect(
()->new TreeMap<Integer,List<T>>(){
private static final long serialVersionUID = 1L;
public String toString(){
return entrySet().stream()
.map( e -> (Stream<String>)e.getValue().stream().map(
v -> e.getKey().toString() + " - " + v.toString()
+ " (" + propertyExtractor.apply(v) + ")" ) )
.flatMap(Function.identity())
.collect(joining("\n"));
}
},
(rank,entry) ->
rank.put(rank.isEmpty()?1:rank.lastKey()+
rank.get(rank.lastKey()).size(),
entry.getValue() ),
(rank1,rank2) -> {
int lastRanking = rank1.lastKey();
int offset = lastRanking + rank1.get(lastRanking).size()-1;
if( propertyExtractor.apply(rank1.get(lastRanking).get(0))
== propertyExtractor.apply(rank2.get(rank2.firstKey()).get(0)) ){
rank1.get(lastRanking).addAll(rank2.get(rank2.firstKey()));
rank2.remove(rank2.firstKey());
}
rank2.forEach((r,items) -> {rank1.put(offset+r, items);} );
}
)
);
}
/**
*
* @param stream
* @param propertyExtractor
* @param propertyComparator
* @return
*/
static <T,V> SortedMap<Integer,List<T>>
rank(Stream<T> stream, Function<T,V> propertyExtractor, Comparator<V> propertyComparator){
return
stream.sorted(comparing(propertyExtractor,propertyComparator))
.collect(TreeMap::new,
(rank, item) -> {
V property = propertyExtractor.apply(item);
if(rank.isEmpty()){
rank.put(new Integer(1),new LinkedList<T>());
}else{
Integer r = rank.lastKey();
List<T> items = rank.get(r);
if(! property.equals(propertyExtractor.apply(items.get(0)))) {
rank.put(r+items.size(), new LinkedList<T>());
}
}
rank.get(rank.lastKey()).add(item);
},
(rank1, rank2) -> {
int lastRanking = rank1.lastKey();
int offset = lastRanking + rank1.get(lastRanking).size()-1;
if( propertyExtractor.apply(rank1.get(lastRanking).get(0))
== propertyExtractor.apply(rank2.get(rank2.firstKey()).get(0)) ){
rank1.get(lastRanking).addAll(rank2.get(rank2.firstKey()));
rank2.remove(rank2.firstKey());
}
rank2.forEach((r,items) -> {rank1.put(offset+r, items);} );
}
);
}
}