Java 日期类 NullPointerException

Question

我正在尝试设置并返回字符串中的最早日期，并且我认为在设置日期时遗漏了一些内容，因为每当我尝试设置日期的值时，我都会收到 nullreferenceexception。感谢您的帮助

private static Date createDate(String input)
{
    Date date = null;

    if (input == null)
        return null;

    // Split formatted input into separate values
    String tempDates[] = input.split(dateSep);

    // Store values as integers
    int[] dateValues = {0, 0, 0};
    dateValues[0] = Integer.parseInt(tempDates[0]);
    dateValues[1] = Integer.parseInt(tempDates[1]);
    dateValues[2] = Integer.parseInt(tempDates[2]);

    // Sort integers from lowest to highest
    Arrays.sort(dateValues);

    // Set return date
    date.setMonth(dateValues[0]);
    date.setDate(dateValues[1]);
    date.setYear(dateValues[2]);


    System.out.println(date);
    // Checking basic date restrictions
    if (date.getMonth() <= 0 || date.getMonth() > 12)
        throw new IllegalArgumentException("Month is not valid " + month);

    if (date.getDay() <= 0 || date.getDay() > 31)
        throw new IllegalArgumentException("Day is not valid " + day);

    if (date.getYear() <= 0)
        throw new IllegalArgumentException("Year is not valid " + year);


    return date;
}

}

Answer 1

您需要初始化Date对象。
将此行更改为 Date date = null; 为 Date date = new Date();。

通常你会得到NullPointerException

When you attempts to use null in a case where an object is required. These include:
1.Calling the instance method of a null object.
2.Accessing or modifying the field of a null object.
3.Taking the length of null as if it were an array.
4.Accessing or modifying the slots of null as if it were an array.
5.Throwing null as if it were a Throwable value.