java8将三维List转为一维List

可以使用流操作和flatMap方法将三维List转为一维List。具体代码如下：

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

public class Main {
    public static void main(String[] args) {
        List<List<List<Integer>>> threeDimList = Arrays.asList(
                Arrays.asList(
                        Arrays.asList(1, 2, 3),
                        Arrays.asList(4, 5, 6)
                ),
                Arrays.asList(
                        Arrays.asList(7, 8, 9),
                        Arrays.asList(10, 11, 12)
                )
        );

        List<Integer> oneDimList = threeDimList.stream()
                .flatMap(List::stream)
                .flatMap(List::stream)
                .collect(Collectors.toList());

        System.out.println(oneDimList);
    }
}

输出结果为：[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12