Java Date类的compareTo()方法比较两个日期并将它们排序。
用法:
public int compareTo(Date anotherDate)
参数：该函数接受单个参数anotherDate，该参数指定要比较的日期。
返回值：该函数提供以下指定的三个返回值：
如果参数Date等于此Date，则返回值0。
如果此Date在Date参数之前，则返回小于0的值。
如果此Date在Date参数之后，则返回大于0的值。
异常：如果anotherDate为null，则该函数引发一个异常，该异常为NullPointerException。
下面的程序演示了上述功能：
// Java code to demonstrate
// compareTo() function of Date class
import java.util.Date;
import java.util.Calendar;
public class GfG {
// main method
public static void main(String[] args)
{
// creating a Calendar object
Calendar c = Calendar.getInstance();
// set Month
// MONTH starts with 0 i.e. ( 0 - Jan)
c.set(Calendar.MONTH, 11);
// set Date
c.set(Calendar.DATE, 05);
// set Year
c.set(Calendar.YEAR, 1996);
// creating a date object with specified time.
Date dateOne = c.getTime();
System.out.println("Date 1: "
+ dateOne);
// creating a date of object
// storing the current date
Date currentDate = new Date();
System.out.println("Date 2: "
+ currentDate);
// compares
System.out.println("On Comparison: "
+ currentDate
.compareTo(dateOne));
}
}
输出：
Date 1: Thu Dec 05 08:17:55 UTC 1996
Date 2: Wed Jan 02 08:17:55 UTC
On Comparison: 1
// Java code to demonstrate
// compareTo() function of Date class
import java.util.Date;
public class GfG {
// main method
public static void main(String[] args)
{
// creating a date of object
// stospecified datent date
Date currentDate = new Date();
System.out.println("Date 1: " + currentDate);
// specifiedDate is assigned to null.
Date specifiedDate = null;
System.out.println("Date 2: " + specifiedDate);
System.out.println("Passing null as parameter: ");
try {
// throws NullPointerException
System.out.println(currentDate
.compareTo(specifiedDate));
}
catch (Exception e) {
System.out.println("Exception: " + e);
}
}
}
输出：
Date 1: Wed Jan 02 08:18:02 UTC
Date 2: null
Passing null as parameter:
Exception: java.lang.NullPointerException
