package jTest;

import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.IntStream;

public class StreamTest {
    public static void main(String[] args) {
        // 创建二维数组
        List<List<String>> list1 = Arrays.asList(
                Arrays.asList("a", "b", "c"),
                Arrays.asList("a", "b", "c")
        );
        // 二维数组平整化
        List<String> list = list1.stream().flatMap(List::stream).toList();
        System.out.println(list);// [a, b, c, a, b, c]

        // peek可以用来调试也可以塞对象，不改变流，如果你这个里面有对象，比如xxx.setXXX() 那么也会修改这个对象
        List<String> list2 = list.stream().filter(s -> s.startsWith("a"))
                .peek(System.out::println)
                .map(String::toUpperCase).toList();
        System.out.println(list2);// [A, A]

        // 求和
        int sum = IntStream.of(1, 2, 3, 4, 5, 6, 7, 8, 9, 10).sum();
        System.out.println(sum);

        // Map集合
        Map<String, Integer> counts = new HashMap<>();
        counts.put("apple", 1);
        counts.put("banana", 1);
        System.out.println(counts);

        counts.compute("apple", (key, val) -> val == null ? 1 : val + 1);
        System.out.println(counts);
    }
}