? ? ?初始化List
? ? ?List<string> list = new ArrayList<string><string>(); ?
? ? ?list.add("string1"); ?
? ? ?list.add("string2"); ?
? ? ?list.add("stringN"); ?
? ??
? ? ?初始化Map
? ? ?Map</String , Object> map = new HashMap</String , Object>(); ?
? ? ?map.put("key1", "value1"); ?
? ? ?map.put("key2", "value2"); ?
? ? ?map.put("keyN", "valueN"); ?

? ? ?初始化List ??
? ? ?List<string> list = new ArrayList<string>(){{ ?
? ? ?add("string1"); ?
? ? ?add("string2"); ?
? ? ?add("stringN"); ? ?}}; ?
? ? ?
? ? ?初始化Map ? ?
? ? ?Map</String , String> map = new HashMap</String , Object>(){{ ?
? ? ?put("keyOne", "valueOne"); ?
? ? ?put("keyTwo", "valueTwo"); ?
? ? ?put("keyThree", "valueThree"); ??
? ? ?}};

? ? ?Map map = Stream.of(1,2,3,4).collect(
? ? ?Collectors.toMap(x -> x, integer -> integer,(key, value) -> value, HashMap::new));
? ? ?System.out.println(JSONObject.toJSONString(map));
? ??
? ? ?List list = Stream.of(1,2,3,4).collect(Collectors.toList());
? ? ?System.out.println(JSONObject.toJSONString(list));

ArrayList<String> list = new ArrayList(Arrays.asList("banana", "milk", "bacon")); ?

public class Student {
?? ?private String name;
?? ?private Integer age;
?? ?private Integer math;
?? ?private Integer english;
?? ?//get set
?? ?public Student(String name, Integer age, Integer math, Integer english) {
?? ??? ?super();
?? ??? ?this.name = name;
?? ??? ?this.age = age;
?? ??? ?this.math = math;
?? ??? ?this.english = english;
?? ?}
?? ?@Override
?? ?public String toString() {
?? ??? ?return "Student [name=" + name + ", age=" + age + ", math=" + math + ", english=" + english + "]";
?? ?}
}

public class StreamDemo {
?? ?List<Student> list = null;
? ? //初始化數(shù)據(jù)
?? ?@Before
?? ?public void beforetest() {
?? ??? ?list = Arrays.asList(new Student("Tom", 18, 88, 90), new Student("Jerry", 20, 77, 89),
?? ??? ??? ??? ?new Student("Lily", 17, 98, 79), new Student("Lucy", 19, 70, 80), new Student("LiLei", 18, 88, 90),
?? ??? ??? ??? ?new Student("HanMeiMei", 21, 87, 79));
?? ?}?
?? ?
?? ?@Test
?? ?public void streamtest() {
?? ??? ?// filter 過濾器返回還是一個stream流對象
?? ??? ?//查詢math成績大于80的學(xué)生并遍歷輸出
?? ??? ?list.stream().filter(e->e.getMath()>80).forEach(System.out::println);//.forEach(e->System.out.println(e))
?? ??? ?//統(tǒng)計數(shù)量count
?? ??? ?System.out.println(list.stream().count());
?? ??? ?//如統(tǒng)計總分大于160的人數(shù)
?? ??? ?System.out.println(list.stream().filter(e->e.getEnglish()+e.getMath()>160).count());
?? ??? ?//limit ?取前n個值
?? ??? ?list.stream().limit(3).forEach(System.out::println);
?? ??? ?//skip 跳過前n個
?? ??? ?list.stream().skip(2).forEach(System.out::println);
?? ??? ?//distinct 去除重復(fù)數(shù)據(jù)
?? ??? ?list.stream().distinct().forEach(System.out::println);
?? ??? ?//map 映射元素可以對元素進行操作 ? 例如對每個學(xué)生年齡加1
?? ??? ?list.stream().map(e->{
?? ??? ??? ?e.setAge(e.getAge()+1);
?? ??? ??? ?return e;
?? ??? ?}).forEach(System.out::println);
?? ??? ?//sorted 排序?
?? ??? ?//升序
?? ??? ?list.stream().sorted((a,b)->{
?? ??? ??? ?return a.getEnglish().compareTo(b.getEnglish());
?? ??? ?});
?? ??? ?//降序
?? ??? ?list.stream().sorted((a,b)->{
?? ??? ??? ?return b.getEnglish().compareTo(a.getEnglish());
?? ??? ?});
?? ??? ?//返回第一個元素 ?
?? ??? ?Optional<Student> first = list.stream().findFirst();
?? ??? ?System.out.println(first.get());
?? ??? ?//返回任意一個元素
?? ??? ?System.out.println(list.stream().findAny().get());
?? ??? ?//anyMatch 是否匹配任意一元素 ?檢查是否包含名字為Tom的
?? ??? ?System.out.println(list.stream().anyMatch(e->e.getName().equals("Tom")));
?? ??? ?//allMatch 是否匹配所有元素
?? ??? ?System.out.println(list.stream().allMatch(e->e.getName().equals("Tom")));
?? ??? ?//noneMatch ?是否未匹配所有元素
?? ??? ?System.out.println(list.stream().noneMatch(e->e.getName().equals("Tom")));
?? ??? ?//findFirst 返回元素中第一個值
?? ??? ?Student student = list.stream().findFirst().get();
?? ??? ?//findAny 返回元素中任意一個值
?? ??? ?Student student1 = list.stream().findAny().get();
?? ??? ?//max 返回最大值 查詢英語成績最高的學(xué)生
?? ??? ?Student student2 = list.stream().max((l1,l2)->l2.getEnglish().compareTo(l1.getEnglish())).get();
?? ??? ?//min 最小值 ?將上面l1，l2位置對調(diào)
?? ??? ?Student student3 = list.stream().max((l1,l2)->l2.getEnglish().compareTo(l1.getEnglish())).get();
?? ??? ?//將流對象轉(zhuǎn)為list?
?? ??? ?list.stream().filter(e->e.getMath()>80).collect(Collectors.toList());
?? ??? ?//將流轉(zhuǎn)未set
?? ??? ?list.stream().filter(e->e.getMath()>80).collect(Collectors.toSet());
?? ??? ?//對對象中的某項進行統(tǒng)計
?? ??? ?IntSummaryStatistics c = list.stream().collect(Collectors.summarizingInt(Student::getEnglish));
?? ??? ?System.out.println(c);//IntSummaryStatistics{count=6, sum=507, min=79, average=84.500000, max=90}
?? ?}? ?
}