获取Stream流

集合

ArrayList<String> s = new ArrayList<>();
Stream<String> stream = s.stream();

map

Map map = new HashMap();
Stream s1 = map.keySet().stream();
Stream s2 = map.values().stream();
Stream s3 = map.entrySet().stream();

 数组

String[] a={"11","222"};
Stream<String> s1 = Stream.of(a);
Stream<String> s2 = Arrays.stream(a);

方法

filter--对流中的数据进行过滤

ArrayList<Integer> s = new ArrayList<>();
s.add(10);
s.add(11);
s.add(9);
s.stream().filter(w -> w>10).forEach(q-> System.out.println(q));

 sorted--对流中的数据进行升序排序

ArrayList<Integer> s = new ArrayList<>();
s.add(10);
s.add(11);
s.add(9);
s.stream().sorted().forEach(q-> System.out.println(q));

//对象降序
ArrayList<Student> s = new ArrayList<>();
s.stream().sorted((o1,o2)->o2.getSum-o1.getSum).forEach(w-> System.out.println(w.getSum()));

limit--获得前几个元素

ArrayList<Integer> s = new ArrayList<>();
s.add(10);
s.add(11);
s.add(9);
s.stream().limit(2).forEach(q-> System.out.println(q));

skip--跳过前几个

 

ArrayList<Integer> s = new ArrayList<>();
s.add(10);
s.add(11);
s.add(9);
s.stream().skip(2).forEach(q-> System.out.println(q));

map--映射

s.stream().map(s::s.getName).forEach(System.out::println);

distinct--去重

去重自定义对象，要重写equals与hashCode

concat--合并流

Stream<String> s1 = Stream.of("12", "23", "45");
Stream<String> s2 = Stream.of("11", "56");
Stream<String> s3 = Stream.concat(s1, s2);
s3.forEach(System.out::println);

reduce 

 Integer sum = integers.reduce(0, Integer::sum);  
//sum，min，max，average

终结流

foreach--遍历

count--统计数量

students.stream().count();

max--最大值

Student s = students.stream().max((o1,o2)-> Double.compare(o1.getHeight(),o2.getHeight())).get();

min--最小值

collect()--将流收集到一个指定集合中取

List<student> students1 = students.stream(),filter(a -> a.getHeight()>170).collect(collectors.tolist())

Map<String,Double> map =
students.stream().filter(a->a.getHeight()>170)
.collect(Collectors.toMap(a ->a.getName(),a -> a.getHeight()));

 

toArrys()--将数组收集到一个数组中

Studentllarr=students.stream().filter(aSystem.out.println(Arrays.tostring(arr));
->a.getHeight()>170).tqArray(len -> new Student[len]);