java8新特性专题之五、创建Stream

1、Stream.of 可变参数

Stream<String> stream1 = Stream.of("A", "B", "C");
System.out.println("stream1:" + stream1.collect(joining()));

程序输出：

stream1:ABC

2、Stream.of 数组

String[] values = new String[]{"A", "B", "C"};
Stream<String> stream2 = Stream.of(values);
System.out.println("stream2:" + stream2.collect(joining()));

程序输出：

stream2:ABC

看 Stream.of 源码，上面这两种方式其实就是第三种方式的包装版。

public static<T> Stream<T> of(T... values) {
    return Arrays.stream(values);
}

我们直接使用源码中的方式也是一样的。

3、Arrays.stream

String[] values = new String[]{"A", "B", "C"};
Stream<String> stream3 = Arrays.stream(values);
System.out.println("stream3:" + stream3.collect(joining()));

程序输出：

stream3:ABC

4、List

List<String> list = Arrays.asList("A", "B", "C");
Stream<String> stream4 = list.stream();
System.out.println("stream4:" + stream4.collect(joining()));

程序输出：

stream4:ABC

5、Set

Set<String> set = new HashSet<>(Arrays.asList("A", "B", "C"));
Stream<String> stream5 = set.stream();
System.out.println("stream5:" + stream5.collect(joining()));

程序输出：

stream5:ABC

6、Map

Map<String, String> map = new HashMap<>();
map.put("1", "A");
map.put("2", "B");
map.put("3", "C");
Stream<String> stream6 = map.values().stream();
System.out.println("stream6:" + stream6.collect(joining()));

程序输出：

stream6:ABC

7、Stream.iterate

Stream<String> stream7 = Stream.iterate("A", e -> String.valueOf((char) (e.charAt(0) + 1))).limit(3);
System.out.println("stream7:" + stream7.collect(joining()));

程序输出：

stream7:ABC

8、Pattern

String value = "A B C";
Stream<String> stream8 = Pattern.compile("\\W").splitAsStream(value);
System.out.println("stream8:" + stream8.collect(joining()));

程序输出：

stream8:ABC

9、Files.lines

try {
    Stream<String> stream9 = Files.lines(Paths.get("d:/data.txt"));
    System.out.println("stream9:" + stream9.collect(joining()));
} catch (IOException e) {
    e.printStackTrace();
}

data.txt文件内容如下：

A
B
C

程序输出：

stream9:ABC

10、Stream.generate

Stream<String> stream10 = Stream.generate(() -> "A").limit(3);
System.out.println("stream10:" + stream10.collect(joining()));

程序输出：

stream10:AAA

本文原创首发于微信公众号：Java技术栈（id:javastack），转载请原样保留本信息。

来源：https://www.cnblogs.com/javastack/p/11199897.html