如何获得今年Java过去月份的列表？

问题描述

我正在使用PhilJay / MPAndroidChart android库中的SingleLine图表，并且需要本年度过去月份的列表。例如，从一月到十月，但是什么时候是十月，那么从一月到十一月，依此类推。 我尝试了这些：Getting List of Month for Past 1 year in Android dynamically， 和Calculate previous 12 months from given month - SimpleDateFormat 但是所有这些大概都用了12个月，我想从今年开始算起

@SuppressLint("SimpleDateFormat")
private void handleXAxis() {
    List<String> allDates = new ArrayList<>();
    String maxDate = "Jan";
    SimpleDateFormat monthDate = new SimpleDateFormat("MMM");
    Calendar cal = Calendar.getInstance();
    try {
        cal.setTime(Objects.requireNonNull(monthDate.parse(maxDate)));
    } catch (ParseException e) {
        e.printStackTrace();
    }
    for (int i = 1; i <= 12; i++) {
        String month_name1 = monthDate.format(cal.getTime());
        allDates.add(month_name1);
        cal.add(Calendar.MONTH,-1);
    }
}

解决方法

tl; dr⇒java.time

直到（包括）当前月份为List<YearMonth>的月份：

public static List<YearMonth> getMonthsOfCurrentYear() {
    YearMonth currentMonth = YearMonth.now();
    List<YearMonth> yearMonths = new ArrayList<>();
    
    for (int month = 1; month <= currentMonth.getMonthValue(); month++) {
        yearMonths.add(YearMonth.of(currentMonth.getYear(),month));
    }
    
    return yearMonths;
}

直到（包括）当前月份为List<String>的月份：

public static List<String> getMonthNamesOfCurrentYear() {
    YearMonth currentMonth = YearMonth.now();
    List<String> yearMonths = new ArrayList<>();
    
    for (int month = 1; month <= currentMonth.getMonthValue(); month++) {
        yearMonths.add(YearMonth.of(currentMonth.getYear(),month)
                                .format(DateTimeFormatter.ofPattern("MMM",Locale.ENGLISH)));
    }
    
    return yearMonths;
}

或者，您可以使用Month的显示名称，而不要使用DateTimeFormatter.ofPattern("MMM")

public static List<String> getMonthNamesOfCurrentYear() {
    YearMonth currentMonth = YearMonth.now();
    List<String> yearMonths = new ArrayList<>();
    
    for (int month = 1; month <= currentMonth.getMonthValue(); month++) {
        yearMonths.add(Month.of(month)
                            .getDisplayName(TextStyle.SHORT,Locale.ENGLISH));
    }
    
    return yearMonths;
}

第二个和第三个示例的输出：

Jan,Feb,Mar,Apr,May,Jun,Jul,Aug,Sep,Oct

像调用时一样

System.out.println(String.join(",",getMonthNamesOfCurrentYear()));