Google Guava--Guava新增集合

Multiset

Multiset 虽然带了个set但是却允许重复元素，与set相同的是不保证元素顺序。

使用场景：获取文章中单词的出现次数

        String[] wordArr = new String[]{"a","b","c","a","a","c","e"};
        List<String> wordsList = Arrays.asList(wordArr);
        Multiset<String> wordsMultiset = HashMultiset.create();
        wordsMultiset.addAll(wordsList);

        for(String key:wordsMultiset.elementSet()){
            System.out.println(key+" count："+wordsMultiset.count(key));
        }
//e count：1
//b count：1
//c count：2
//a count：3

Multimap

Multiset 实现了类似 Map<K, List> 的数据结构

        Multimap<String, Integer> multimap = ArrayListMultimap.create();
        for (int i = 0; i < 10; i++) {
            Random random = new Random();
            multimap.put("1", random.nextInt());
        }
        System.out.println(multimap.size()); //10
        System.out.println(multimap.keys()); //[1 x 10]
        for (int i = 0; i < 5; i++) {
            Random random = new Random();
            multimap.put("2", random.nextInt());
        }
        System.out.println(multimap.size()); //15
        System.out.println(multimap.keys()); //[2 x 5, 1 x 10]
        for (String x : multimap.keySet()) {
            System.out.println(x+" : ");
            Map<String, Collection<Integer>> listMap = multimap.asMap();
            Collection<Integer> collection = listMap.get(x);
            for (Integer i : collection) {
                System.out.println(i);
            }
        }

BiMap

BiMap提供了一种新的集合类型，它提供了key和value的双向关联的数据结构。 BiMap 要求Value是唯一的，Value重复会抛出错误

        BiMap<Integer,String> bimap = HashBiMap.create();
        bimap.put(1,"1");
        bimap.put(2,"2");
        bimap.put(3,"3");
        bimap.put(2,null);

        BiMap<String,Integer> valueMap = bimap.inverse();
        System.out.println(valueMap.get("3")); //3

        bimap.forcePut(4,"1"); //强制插入会覆盖重复Value的Key
        System.out.println(valueMap.get("1")); //4

Table

Table 实现了类似Map<rowId, Map<columId, Value>> 及 可以 通过row 来查找也可以通过 colum来查找

        Table<Integer, String,Integer> table = HashBasedTable.create();
        table.put(1,"lilei",23);
        table.put(2,"hanmeimei",24);
        table.put(3,"lilei",3);
        table.put(3,"lily",18);

        Map<String, Integer> row = table.row(3);
        System.out.println(row);                               //{lily=18, lilei=3}
        Map<Integer, Integer> column = table.column("lilei");
        System.out.println(column);                           //{1=23, 3=3}

RangeSet

RangeSet描述了一组不相连的、非空的区间。当把一个区间添加到可变的RangeSet时，所有相连的区间会被合并，空区间会被忽略。

    RangeSet<Integer> rangeSet = TreeRangeSet.create();
    rangeSet.add(Range.closed(1, 5));
    System.out.println(rangeSet);     //[[1‥5]]

    rangeSet.add(Range.closedOpen(5, 10));
    System.out.println(rangeSet);     //[[1‥10)]

    rangeSet.add(Range.closedOpen(8, 10));
    System.out.println(rangeSet);    //[[1‥10)]

    rangeSet.add(Range.openClosed(10, 15));
    System.out.println(rangeSet);   //[[1‥10), (10‥15]]

    rangeSet.remove(Range.open(8, 12));
    System.out.println(rangeSet);   //[[1‥8], [12‥15]]