官方文档如下链接
https://docs.spring.io/spring-boot/docs/2.3.3.RELEASE/reference/htmlsingle/#deployment-initd-service
curl -L https://get.daocloud.io/docker/compose/releases/download/1.25.0/docker-compose-`uname -s`-`uname -m` > /usr/local/bin/docker-compose;
chmod +x /usr/local/bin/docker-compose;
在Java 8中,Stream可以容纳不同的数据类型,例如:
Stream<String[]>
Stream<Set<String>>
Stream<List<String>>
Stream<List<Object>>
但是,Stream和collectors中的有些操作不能支持Stream中包含的复合类型,如filter
、sum
、distinct
等,不能直接操作这些复合类型。
所以我们需要使用flatMap()
(flat是水平的;平坦的;平滑的意思,用在这里就是把多层的数据结构变成单层(平的)数据结构)进行转换。
Stream<String[]> -> flatMap -> Stream<String>
Stream<Set<String>> -> flatMap -> Stream<String>
Stream<List<String>> -> flatMap -> Stream<String>
Stream<List<Object>> -> flatMap -> Stream<Object>
#换成数据是下面这个样子
{{1,2},{3,4},{5,6}} -> flatMap -> {1,2,3,4,5,6}
{'a','b'},{'c','d'},{'e','f'}} -> flatMap -> {'a','b','c' 'd', 'e', 'f'}
String[][] data = new String[][]{{"a", "b"}, {"c", "d"}, {"e", "f"}};
//Stream<String[]>
Stream<String[]> temp = Arrays.stream(data);
//Stream<String>, GOOD!
Stream<String> stringStream = temp.flatMap(x -> Arrays.stream(x));
Stream<String> stream = stringStream.filter(x -> "a".equals(x.toString()));
stream.forEach(System.out::println);
public class Student {
private String name;
private Set<String> book;
public void addBook(String book) {
if (this.book == null) {
this.book = new HashSet<>();
}
this.book.add(book);
}
//getters and setters
}
Student obj1 = new Student();
obj1.setName("mkyong");
obj1.addBook("Java 8 in Action");
obj1.addBook("Spring Boot in Action");
obj1.addBook("Effective Java (2nd Edition)");
Student obj2 = new Student();
obj2.setName("zilap");
obj2.addBook("Learning Python, 5th Edition");
obj2.addBook("Effective Java (2nd Edition)");
List<Student> list = new ArrayList<>();
list.add(obj1);
list.add(obj2);
List<String> collect =
list.stream()
.map(x -> x.getBook()) //Stream<Set<String>>
.flatMap(x -> x.stream()) //Stream<String>
//去重
.distinct()
.collect(Collectors.toList());
collect.forEach(x -> System.out.println(x));
代码:
String[] words = new String[]{"Hello","World"};
List<String> a = Arrays.stream(words)
.map(word -> word.split(""))
.flatMap(Arrays::stream)
.distinct()
.collect(toList());
a.forEach(System.out::print);
结果输出:HeloWrd
使用flatMap方法的效果是,各个数组并不是分别映射一个流,而是映射成流的内容,所有使用map(Array::stream)时生成的单个流被合并起来,即扁平化为一个流。
要获取Jar
中的文件不能使用ResourceUtils.getFile()
来获取文件,因为被打成了Jar
文件。
只能通过流来获取。如下:
- ClassPathResource
ClassPathResource resource = new ClassPathResource("videoToM3u8.lua");
InputStream stream = resource.getInputStream();
- ResourceLoader
ResourceLoader loader = new DefaultResourceLoader();
Resource res = loader.getResource("classpath:videoToM3u8.lua");
InputStream inputStream = res.getInputStream();