? ? ?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(gè)stream流對(duì)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(jì)數(shù)量count
?? ??? ?System.out.println(list.stream().count());
?? ??? ?//如統(tǒng)計(jì)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(gè)值
?? ??? ?list.stream().limit(3).forEach(System.out::println);
?? ??? ?//skip 跳過前n個(gè)
?? ??? ?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(duì)元素進(jìn)行操作 ? 例如對(duì)每個(gè)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(gè)元素 ?
?? ??? ?Optional<Student> first = list.stream().findFirst();
?? ??? ?System.out.println(first.get());
?? ??? ?//返回任意一個(gè)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(gè)值
?? ??? ?Student student = list.stream().findFirst().get();
?? ??? ?//findAny 返回元素中任意一個(gè)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(duì)調(diào)
?? ??? ?Student student3 = list.stream().max((l1,l2)->l2.getEnglish().compareTo(l1.getEnglish())).get();
?? ??? ?//將流對(duì)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(duì)對(duì)象中的某項(xiàng)進(jìn)行統(tǒng)計(jì)
?? ??? ?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}
?? ?}? ?
}