近くにGava(三):集合

集合:
FlouentIterable類:

FlouentIterable.filterフィルタリング、すなわちPredicateを用いて実現される:

Iterable<Person> adults = FluentIterable.from(ps).filter(
	new Predicate<Person>() {
		@Override
		public boolean apply(Person p) {
			return p.getAge() >= 18; //   >18
		}
	});

FlouentIterable.tranform()変換を使用して、Functionを利用して実現します.

 FluentIterable.from(ps).transform(new Function<Person, String>() {
	@Override
	public String apply(Person p) {
	     return Joiner.on('#').join(p.getName(), p.getAge());
	}
});

Listsクラス:

Lists.newArayListを用いてリストを作成する:

ps = Lists.newArrayList(
	new Person("person1", 22),
	new Person("person2", 23),
	new Person("person3", 17)
);

Lists.partition()を使用してリストを分割します.

//[a, b, c, d, e] --> [[a, b], [c, d, e]] -
List<List<Person>> subList = Lists.partition(ps, 2);

Setsクラス:

Sets.difference()はS 1-S 2

を求めます.

Set<String> s1 = Sets.newHashSet("1", "2", "3");
Set<String> s2 = Sets.newHashSet("2", "3", "4");
Sets.difference(s1, s2); //[1]

Sets.intersection()はS 1を求めて、S 2は

を交差させます.

Set<String> s1 = Sets.newHashSet("1", "2", "3");
Set<String> s2 = Sets.newHashSet("3", "2", "4");
Sets.SetView<String> sv = Sets.intersection(s1, s2); // [2, 3]

Sets.union()は、合計

を求めます.

Set<String> s1 = Sets.newHashSet("1", "2", "3");
Set<String> s2 = Sets.newHashSet("3", "2", "4");
Sets.SetView<String> sv = Sets.union(s1, s2); // [3, 2, 1 ,4]

Mapsクラス:

Maps.uniqueIndex()リストをmap

に変換する.

//iterator      Map.values, key Function.apply   
Maps.uniqueIndex(ps.iterator(), new Function<Person, String>() {
	@Override
	public String apply(Person p) {
		return p.getName();
	}
});

Maps.asMap()とMaps.uniqueIndex()は逆

です.

Maps.asMap(ps, new Function<Person, String>() {
	@Override
	public String apply(Person p) {
		return p.getName();
	}
});

Maps Transform API:

Maps.transformEntries(map, new Maps.EntryTransformer<String, Boolean, String>() {
    @Override
    public String transformEntry(String key, Boolean value) {
        return value ? "yes" : "no";
    }
});  Map<String, Boolean> --> Map<String, String>,      Maps.transformValues   

Multimaps:

個のキーは複数のvalueに対応する.

ArayListMultiMap:

ArrayListMultimap<String, String> multiMap = ArrayListMultimap.create();
multiMap.put("Foo", "1");
multiMap.put("Foo", "2");
multiMap.put("Foo", "3");
System.out.println(multiMap); // {Foo=[1,2,3]}

重複値が発生すると、ArayListMultiMapのvalueの時にArayListが追加されます.

ArrayListMultimap<String, String> multiMap = ArrayListMultimap.create();
multiMap.put("Bar", "1");
multiMap.put("Bar", "2");
multiMap.put("Bar", "3");
multiMap.put("Bar", "3");
multiMap.put("Bar", "3");
System.out.println(multiMap); //{Bar=[1, 2, 3, 3, 3]}，   value   ，value     List

HashMultiMap:

HashMultimap<String, String> multiMap = HashMultimap.create();
multiMap.put("Bar", "1");
multiMap.put("Bar", "2");
multiMap.put("Bar", "3");
multiMap.put("Bar", "3");
multiMap.put("Bar", "3");
System.out.println(multiMap); //{Bar=[3, 2, 1]},    value    ，value     Set

他のいくつかのMultiMap:

LinkedHashMultimap //   HashMultimap,   LinkedHashMap
TreeMultimap //    MultiMap,   TreeMap
//      map
ImmutableListMultimap
ImmutableMultimap
ImmutableSetMultimap

BiMap:

その制限valueは唯一であり、valueを通じてkey

を見つけることができる.

BiMap<String,String> biMap = HashBiMap.create();
biMap.put("1","Tom");         
biMap.put("2","Tom"); //    

BiMap.forcePut()を強制的にvalue等しいentryに入れる:

BiMap<String, String> biMap = HashBiMap.create();
biMap.put("1", "Tom");
biMap.forcePut("2", "Tom");
System.out.println(biMap); //{2=Tom}

BiMap.inverse()逆転key-value

BiMap<String, String> biMap = HashBiMap.create();
biMap.put("1", "Tom");
biMap.put("2", "Harry");
BiMap<String, String> inverseMap = biMap.inverse();
System.out.println(biMap); //{2=Harry, 1=Tom}
System.out.println(inverseMap); //{Harry=2, Tom=1

テーブル:

は、2つのkey[行,列]を有し、1つの値に対応する.

Hash BasedTable:

汎用動作

HashBasedTable<Integer, Integer, String> table = HashBasedTable.create();
table.put(1, 1, "Rook");
table.put(1, 2, "Knight");
table.put(1, 3, "Bishop");
System.out.println(table.contains(1, 1)); //true
System.out.println(table.containsColumn(2)); //true
System.out.println(table.containsRow(1)); //true
System.out.println(table.containsValue("Rook")); //true
System.out.println(table.remove(1, 3)); //Bishop
System.out.println(table.get(3, 4)); //null

Table view、テーブル行列図

Map<Integer,String> columnMap = table.column(1);
Map<Integer,String> rowMap = table.row(2);

他のテーブル

ArrayTable //      
ImmutableTable //   table，       
TreeBasedTable //      table

Range:

は範囲のクラスを表します.

Range<Integer> numberRange = Range.closed(1, 10); //    
System.out.println(numberRange.contains(10)); //true
System.out.println(numberRange.contains(1)); //true
		
Range<Integer> numberRange1 = Range.open(1,10); //    
System.out.println(numberRange1.contains(10)); //false
System.out.println(numberRange1.contains(1)); //false

RangeとFunctionは、Predicateのフィルタリング条件

に組み合わされる.

Range<Integer> ageRange = Range.closed(35, 50);
//Person age   function
Function<Person, Integer> ageFunction = new Function<Person, Integer>() {
	@Override
	public Integer apply(Person person) {
		return person.getAge();
	}
};
//       [35, 50]    
Predicate<Person> predicate = Predicates.compose(ageRange,ageFunction);

可変ではないセット

を作成します.

MultiMap<Integer,String> map = new ImmutableListMultimap.Builder<Integer,String>()
                                   .put(1,"Foo").putAll(2,"Foo","Bar","Baz")
                                   .putAll(4,"Huey","Duey","Luey")
                                   .put(3,"Single").build();

Ordering:

Orderingは、簡単で強力な並べ替え機能を提供する.

/**
 *        
 */
public class CityByPopluation implements Comparator<City> {
	@Override
	public int compare(City city1, City city2) {
		return Ints.compare(city1.getPopulation(), city2.getPopulation());
	}
}

逆順

Ordering.from(cityByPopluation).reverse();

処理Null

Ordering.from(comparator).nullsFirst();//null       

二次並べ替え

/**
 *      
 */
public class CityByRainfall implements Comparator<City> {
	@Override
	public int compare(City city1, City city2) {
		return Doubles.compare(city1.getAverageRainfall(),
				city2.getAverageRainfall());
	}
}

Ordering<City> secondaryOrdering = Ordering.from(cityByPopulation).compound(cityByRainfall);//     
Collections.sort(cities,secondaryOrdering); //  

最大最小

を取得します.

Ordering<City> ordering = Ordering.from(cityByPopluation);
List<City> topFive = ordering.greatestOf(cityList,5); // 5 
List<City> bottomThree = ordering.leastOf(cityList,3); //  3 

見たところGavaは集合の方面でやはりとても力があります.
指摘を惜しまない.