通过 java 8 获取和编辑子列表在主列表中

Question

我有很多主列表，其中有一个子列表。如何访问子列表并通过java 8进行编辑。例子。List<Student> list = ....; list[0]  = {id = 1, name = "aa", ListMinute = List<String> ls1}list[1]  = {id = 2, name = "bb", ListMinute = List<String> ls2}list[2]  = {id = 3, name = "cc", ListMinute = List<String> ls3}list[3]  = {id = 4, name = "dd", ListMinute = List<String> ls4}list[0] 的子列表示例：List<String> ls1 = {"120", "150", "45", "195"}; //List in minutes.如何将所有子列表从分钟转换为小时和分钟。list[0] 的子列表的输出：List<String> ls1 = {"2", "2.30", "0.45", "3.15"}; // List in hours and minutes.

Answer 1

获得转换的方法之一可能是：

List<String> ls1 = List.of("120", "150", "45", "195"); //List in minutes.

List<String> out = ls1.stream()

         .mapToInt(Integer::parseInt)

         .mapToObj(min -> String.format("%d.%d", min / 60, min % 60)) 

         .collect(Collectors.toList());

// would output 2.0 instead of 2 though

如果你想更新你现有的List，你可以试试replaceAll

List<String> ls1 = Stream.of("120", "150", "45", "195").collect(Collectors.toList()); //List in minutes.

ls1.replaceAll(a -> {

    int min = Integer.parseInt(a);

    return String.format("%d.%d", min / 60, min % 60);

});

Answer 2

您可以像这样修改您的list实例replaceAll

list.stream()

        .map(Student::getListMinute)

        .forEach(minutes ->

                minutes.replaceAll(min -> format("%d.%d", parseInt(min) / 60, parseInt(min) % 60))

        );