Java8 流操作

String[] strs = {"34020000002000000001", "34020000002000000002", "34020000002000000003", "34020000002000000004"};
        List<String> collect = Arrays.stream(strs).map(a -> a.split("")).flatMap(Arrays::stream).collect(Collectors.toList());
        System.out.println(collect);

        List<String> collect2 = Arrays.stream(strs).map(a -> a.split("")).flatMap(Arrays::stream).distinct().collect(Collectors.toList());
        System.out.println(collect2);

        List<String> collect1 = Arrays.stream(strs).map(a -> a.substring(0, 4)).collect(Collectors.toList());
        System.out.println(collect1);

        String[] words = {"Hello", "World"};
        List<String> a = Arrays.stream(words)
                .map(word -> word.split(""))
                .flatMap(Arrays::stream)
                .distinct()
                .collect(Collectors.toList());
        System.out.println(a);
        a.forEach(System.out::print);

对应的输出结果：

[3, 4, 0, 2, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 1, 3, 4, 0, 2, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 2, 3, 4, 0, 2, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 3, 3, 4, 0, 2, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 4]
[3, 4, 0, 2, 1]
[3402, 3402, 3402, 3402]
[H, e, l, o, W, r, d]
HeloWrd