Java:使用Java.Time to tostring to localdate有问题

Question

我正在处理问题集，并尝试构建返回日期的类。对于这个问题，我需要返回一周中的一天"星期一"，"星期二"给定日期。我在堆栈溢出上搜索，并决定尝试使用Java。Time：

package Chapter1.Section2;
import edu.princeton.cs.algs4.StdIn;
import edu.princeton.cs.algs4.StdOut;
import java.time.*;
import java.time.format.DateTimeFormatter;
import java.time.format.TextStyle;
import java.util.Locale;
public class exercise_1_2_12 {
    private int day;
    private int month;
    private int year;
    public exercise_1_2_12(int month, int day, int year){
        if (!isDateValid(month, day, year)){
            throw new IllegalArgumentException("Invalid Date!");
        }
        this.month = month;
        this.day = day;
        this.year = year;
    }
    public int day(){
        return day;
    }
    public int month(){
        return month;
    }
    public int year(){
        return year;
    }
    public String toString(){
        //return month() + "-" + day() + "-" + year();
        return  year + "/" + String.format("%02d", month) + "/" + 
        String.format("%02d", day);
    }
    public boolean isDateValid(int month, int day, int year) {
        int[] dayInEachMonthLeapYr = {31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
        int[] dayInEachMonthNonLeapYr = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
        boolean valid = true;

        if ((year % 400 == 0) || ((year % 4 == 0) && (year % 100 != 0))) {
            if (year < 1 || month < 1 || month > 12 || day < 1 || day > dayInEachMonthLeapYr[month - 1]) {
                valid = false;
            }
        } else {
            if (year < 1 || month < 1 || month > 12 || day < 1 || day > dayInEachMonthNonLeapYr[month - 1]) {
                valid = false;
            }
        }
        return valid;
    }
    public String dayOfWeekName(){
        DateTimeFormatter format = DateTimeFormatter.ofPattern("mm/dd/yyyy");
        String input = this.toString();
        LocalDate date = LocalDate.parse(input, format);
        DayOfWeek dayOfWeek = date.getDayOfWeek();
        String result = dayOfWeek.getDisplayName(TextStyle.FULL, Locale.US);
        return result;
    }
    public static void main(String[] args){
        StdOut.print("Enter month: ");
        int month = StdIn.readInt();
        StdOut.print("Enter day: ");
        int day = StdIn.readInt();
        StdOut.print("Enter year: ");
        int year = StdIn.readInt();
        exercise_1_2_12 smartDate = new exercise_1_2_12(month,day,year);
        StdOut.println(smartDate);
        smartDate.dayOfWeekName();
    }
}

问题可能是在实例方法dayofweekname((中，我试图将对象解析。要串起格式，然后将其存储在本地日期中，然后返回工作日的名称。我对此进行了测试，错误消息如下：

Enter month: 4
Enter day: 1
Enter year: 2018
2018/04/01
Exception in thread "main" java.time.format.DateTimeParseException: Text '2018/04/01' could not be parsed at index 2
at java.time.format.DateTimeFormatter.parseResolved0(DateTimeFormatter.java:1949)
at java.time.format.DateTimeFormatter.parse(DateTimeFormatter.java:1851)
at java.time.LocalDate.parse(LocalDate.java:400)
at Chapter1.Section2.exercise_1_2_12.dayOfWeekName(exercise_1_2_12.java:64)
at Chapter1.Section2.exercise_1_2_12.main(exercise_1_2_12.java:85)
Process finished with exit code 1

我不太确定如何解决此问题。

Answer 1

请查看您的日期模式：

DateTimeFormatter format = DateTimeFormatter.ofPattern("mm/dd/yyyy");

日期：

'2018/04/01'

自然不匹配它。

要么输入该模式的日期，例如：

'04/01/2018'

或更改模式：

DateTimeFormatter format = DateTimeFormatter.ofPattern("yyyy/MM/dd");

重要： @ivar在注释中精确指出，还请注意，月的模式是大写M 。当您使用mm时，它会匹配分钟。

Answer 2

使用此格式化：

DateTimeFormatter.ofPattern("MM/dd/yyyy")