Java 8 中创建 Stream 的 10 种方式

喜欢ヅ旅行 2022-12-13 01:47 70阅读 0赞

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## Java 8 中创建 Stream 的 10 种方式 ##

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import java.io.IOException;
    import java.nio.file.Files;
    import java.nio.file.Paths;
    import java.util.*;
    import java.util.regex.Pattern;
    import java.util.stream.Stream;
    
    import static java.util.stream.Collectors.joining;
    
    public class Example {
        
    
        public static void main(String[] args) {
        
            //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[] values2 = new String[]{
        "A", "B", "C"};
            Stream<String> stream3 = Arrays.stream(values2);
            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";
            try (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
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
        }
    
    
    
    
    }