2020-12-03 java stream 使用stream 循环List

// streams/CollectionToStream.java
import java.util.*;
import java.util.stream.*;
public class CollectionToStream {
    public static void main(String[] args) {
        List bubbles = Arrays.asList(new Bubble(1), new Bubble(2), new Bubble(3));
        System.out.println(bubbles.stream()
            .mapToInt(b -> b.i)
            .sum());

        Set w = new HashSet<>(Arrays.asList("It's a wonderful day for pie!".split(" ")));
        w.stream()
         .map(x -> x + " ")
         .forEach(System.out::print);
        System.out.println();

        Map m = new HashMap<>();
        m.put("pi", 3.14159);
        m.put("e", 2.718);
        m.put("phi", 1.618);
        m.entrySet().stream()
                    .map(e -> e.getKey() + ": " + e.getValue())
                    .forEach(System.out::println);
    }
}