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package com.hks.lambda;
import org.junit.Test;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;
public class MapReflectTest {
/**
* map 生成的是个 1:1 映射，每个输入元素，都按照规则转换成为另外一个元素。
*/
@Test
public void oneToOneTest(){
List<Integer> nums = Arrays.asList(1, 2, 3, 4);
List<Integer> squareNums = nums.stream().
map(n -> n * n).
collect(Collectors.toList());
squareNums.forEach(System.out::println);
}
/**
* 还有一些场景，是一对多映射关系的，这时需要 flatMap。
*/
@Test
public void oneToManyTest(){
Stream<List<Integer>> inputStream = Stream.of(
Arrays.asList(1),
Arrays.asList(2, 3),
Arrays.asList(4, 5, 6)
);
Stream<Integer> outputStream = inputStream.
flatMap((childList) -> childList.stream());
outputStream.forEach(System.out::println);
}
}