Lambda_10 函数表达式 Stream flatMap

清疚 2022-12-19 13:26 163阅读 0赞

### Lambda\_10 函数表达式 Stream flatMap ###

1.  通过匿名内部类实现业务或lambda表达式
2.  多维度（数组）转换数据
3.  数据结构层级将维

public class Lambda11 { 
        public static void main(String[] args) { 
            List<Integer> listSingle = Arrays.asList(1, 3, 5, 7);
            List<Integer> listDouble = Arrays.asList(2, 4, 6, 8);
            //将 listSingle listDouble 组装成一个二维数组
            System.out.println("打印二维数组数据");
            List<List<Integer>> list = Stream.of(listSingle, listDouble).collect(Collectors.toList());
            list.forEach((List<Integer> listInt) -> { 
                listInt.forEach(t -> System.out.print(t));
                System.out.println("");
            });
    
            //可以简写
            System.out.println("===============简写");
            list.forEach((listInt) -> listInt.forEach(t -> System.out.print(t)));
    
            /** * Stream<List<Integer>> ==转换为 ==> Stream<Integer> * 匿名内部类实现 */
            System.out.println("\n===============匿名内部类实现");
            Stream<Integer> stream = list.parallelStream().flatMap(new Function<List<Integer>, Stream<? extends Integer>>() { 
                @Override
                public Stream<? extends Integer> apply(List<Integer> integers) { 
                    return integers.stream();
                }
            });
            stream.forEach(t -> System.out.print(t));
    
    
            /** * 使用lambda表达式实现 */
            System.out.println("\n===============lambda表达式实现");
            Stream<Integer> streamLambda = list.parallelStream().flatMap((List<Integer> integers) ->{ 
                //Stream<Integer>
                return  integers.stream();
            });
            streamLambda.forEach(t -> System.out.print(t));
    
            System.out.println("\n===============lambda表达式实现 简写 ");
            Stream<Integer> streamLambdaJX = list.parallelStream().flatMap(t -> t.stream());
            streamLambdaJX.forEach(t -> System.out.print(t));
    
    
        }
    }