java - 我正在更改对象的一部分，但它不断更改列表中的所有对象，而不考虑条件集

Question

我试图将每个 CourseGroup 的每个星期一的周期号 1 设置为 true，但对象每天都会更改，而不仅仅是星期一。请查看下面的示例

import java.util.ArrayList;

import java.util.Arrays;

import java.util.List;

import java.util.Objects;

class HelloWorld {



    public static void main(String[] args) {
        SchoolObject schoolObject;
        List<LecturePeriod> lecturePeriods = new ArrayList<>();
        for (int i = 1; i <= 10; i++) {
            String periodName = "Period " + i;
            int periodNo = i;
            boolean isPeriodAllocated = false;
            lecturePeriods.add(new LecturePeriod(periodName, periodNo, isPeriodAllocated));
        }

        List<Day> days = new ArrayList<>();
        for (int i = 1; i <= 5; i++) {
            String dayName;
            switch (i) {
                case 1:
                    dayName = "MONDAY";
                    break;
                case 2:
                    dayName = "TUESDAY";
                    break;
                case 3:
                    dayName = "WEDNESDAY";
                    break;
                case 4:
                    dayName = "THURSDAY";
                    break;
                case 5:
                    dayName = "FRIDAY";
                    break;
                default:
                    dayName = "NONE";
            }

            int dayNo = i;
            days.add(new Day(dayName, dayNo, lecturePeriods));
        }

        List<YearGroup> yearGroups = new ArrayList<>();
        for (int i = 1; i <= 3; i++) {
            int yearGroupNumber = i;
            if (Objects.equals(i, 1)) {
                yearGroups.add(new YearGroup(yearGroupNumber, new ArrayList<>(Arrays.asList(new CourseGroup("Science" + 1, days)))));
            } else if (Objects.equals(i, 2)) {
                yearGroups.add(new YearGroup(yearGroupNumber, new ArrayList<>(Arrays.asList(new CourseGroup("Science" + 2, days)))));
            } else if (Objects.equals(i, 3)) {
                yearGroups.add(new YearGroup(yearGroupNumber, new ArrayList<>(Arrays.asList(new CourseGroup("Science" + 3, days)))));
            }

        }

        schoolObject = new SchoolObject();
        schoolObject.setYearGroups(yearGroups);
        System.out.println("School Object Before Changing Periods="+schoolObject.toString());

        schoolObject.getYearGroups().forEach(yearGroup -> {
            yearGroup.getCourseGroups().forEach(courseGroup -> {
                courseGroup.getDays().forEach(day -> {
                    String dayName = day.getDayName();
                    if (Objects.equals(dayName, "MONDAY")) {
                        day.getLecturePeriods().forEach(lecturePeriod -> {
                            int lecturePeriodNumber = lecturePeriod.getPeriodNumber();
                            if (Objects.equals(lecturePeriodNumber, 1)) {
                                lecturePeriod.setIsPeriodAllocated(true);

                            }
                        });
                    }
                });
            });
        });
        System.out.println("\nSchool Object After Changing Periods=" + schoolObject.toString());
        final int[] numberOfAllocatedPeriodsExpected = {0};
        schoolObject.getYearGroups().forEach(yearGroup -> {
            yearGroup.getCourseGroups().forEach(courseGroup -> {
                courseGroup.getDays().forEach(day -> {
                    day.getLecturePeriods().forEach(lecturePeriod -> {
                        int lecturePeriodNumber = lecturePeriod.getPeriodNumber();
                        if (Objects.equals(lecturePeriodNumber, 1)) {
                            numberOfAllocatedPeriodsExpected[0]++;
                        }
                    });
                });
            });
        });


        System.out.println("\nTest result ="+Objects.equals(numberOfAllocatedPeriodsExpected[0],3));

    }




    public static class SchoolObject {
        List<YearGroup> yearGroups;

        @Override
        public String toString() {
            final StringBuilder sb = new StringBuilder("SchoolObject{");
            sb.append("yearGroups=").append(yearGroups);
            sb.append('}');
            return sb.toString();
        }

        public List<YearGroup> getYearGroups() {
            return yearGroups;
        }

        public void setYearGroups(List<YearGroup> yearGroups) {
            this.yearGroups = yearGroups;
        }
    }

    public static class YearGroup {

        int yearGroupNumber;
        List<CourseGroup> courseGroups;

        public YearGroup(int yearGroupNumber, List<CourseGroup> courseGroups) {
            this.yearGroupNumber = yearGroupNumber;
            this.courseGroups = courseGroups;
        }

        @Override
        public String toString() {
            final StringBuilder sb = new StringBuilder("YearGroup{");
            sb.append("yearGroupNumber=").append(yearGroupNumber);
            sb.append(", courseGroups=").append(courseGroups);
            sb.append('}');
            return sb.toString();
        }

        public int getYearGroupNumber() {
            return yearGroupNumber;
        }

        public void setYearGroupNumber(int yearGroupNumber) {
            this.yearGroupNumber = yearGroupNumber;
        }

        public List<CourseGroup> getCourseGroups() {
            return courseGroups;
        }

        public void setCourseGroups(List<CourseGroup> courseGroups) {
            this.courseGroups = courseGroups;
        }
    }

    public static class CourseGroup {
        String courseGroupName;
        List<Day> days;

        public CourseGroup(String courseGroupName, List<Day> days) {
            this.courseGroupName = courseGroupName;
            this.days = days;
        }

        @Override
        public String toString() {
            final StringBuilder sb = new StringBuilder("CourseGroup{");
            sb.append("courseGroupName='").append(courseGroupName).append('\'');
            sb.append(", days=").append(days);
            sb.append('}');
            return sb.toString();
        }

        public List<Day> getDays() {
            return days;
        }

        public void setDays(List<Day> days) {
            this.days = days;
        }

        public String getCourseGroupName() {
            return courseGroupName;
        }

        public void setCourseGroupName(String courseGroupName) {
            this.courseGroupName = courseGroupName;
        }
    }

    public static class Day {
        String dayName;
        int dayNo;
        List<LecturePeriod> lecturePeriods;

        public Day(String dayName, int dayNo, List<LecturePeriod> lecturePeriods) {
            this.dayName = dayName;
            this.lecturePeriods = lecturePeriods;
            this.dayNo = dayNo;
        }

        @Override
        public String toString() {
            final StringBuilder sb = new StringBuilder("Day{");
            sb.append("dayName='").append(dayName).append('\'');
            sb.append(", dayNo=").append(dayNo);
            sb.append(", lecturePeriods=").append(lecturePeriods);
            sb.append('}');
            return sb.toString();
        }

        public String getDayName() {
            return dayName;
        }

        public void setDayName(String dayName) {
            this.dayName = dayName;
        }

        public int getDayNo() {
            return dayNo;
        }

        public void setDayNo(int dayNo) {
            this.dayNo = dayNo;
        }

        public List<LecturePeriod> getLecturePeriods() {
            return lecturePeriods;
        }

        public void setLecturePeriods(List<LecturePeriod> lecturePeriods) {
            this.lecturePeriods = lecturePeriods;
        }
    }

    public static class LecturePeriod {
        String periodName;
        int periodNumber;
        boolean isPeriodAllocated;

        public LecturePeriod(String periodName, int periodNumber, boolean isPeriodAllocated) {
            this.periodName = periodName;
            this.periodNumber = periodNumber;
            this.isPeriodAllocated = isPeriodAllocated;
        }

        @Override
        public String toString() {
            final StringBuilder sb = new StringBuilder("LecturePeriod{");
            sb.append("periodName='").append(periodName).append('\'');
            sb.append(", periodNumber=").append(periodNumber);
            sb.append(", isPeriodAllocated=").append(isPeriodAllocated);
            sb.append('}');
            return sb.toString();
        }

        public String getPeriodName() {
            return periodName;
        }

        public void setPeriodName(String periodName) {
            this.periodName = periodName;
        }

        public int getPeriodNumber() {
            return periodNumber;
        }

        public void setPeriodNumber(int periodNumber) {
            this.periodNumber = periodNumber;
        }

        public boolean isPeriodAllocated() {
            return isPeriodAllocated;
        }

        public void setIsPeriodAllocated(boolean isPeriodAllocated) {
            this.isPeriodAllocated = isPeriodAllocated;
        }
    }
}

观察数据的输出，您会注意到 schoolObject 将每个 courseGroup 中所有日期的所有 LecturePeriods 设置为 true，而不仅仅是星期一。任何帮助都感激不尽。注意:我尽力将问题提取到最低限度，而不使用 gson 或 jackson，这将在梳理生成的 json 时提供更清晰的输出。为了测试起见，我将所有内容压缩到一个类中。

您可以在此处查看示例 http://ideone.com/3uyE5G

Answer 1

这是因为您为所有日期分配相同的讲座时间引用:

days.add(new Day(dayName, dayNo, lecturePeriods));

因此，每次您在某一天更改 LecturePeriods 对象中的属性时，所有这些属性都会发生更改。为了解决这个问题，每天都必须有自己的 LecturePeriods 实例

List<LecturePeriod> lecturePeriods = new ArrayList<>();
for (int j = 1; j <= 10; j++) {
    lecturePeriods.add(new LecturePeriod("Period " + j, j, false));
}
days.add(new Day(dayName, dayNo, lecturePeriods));