Java如何比较日期类型

这里介绍Java比较两个日期类型三个例子：

Date.compareTo()

一个经典的方法比较两个日期类型。

the value 0 if the argument Date is equal to this Date; a value less than 0 if this Date is before the Date argument; and a value greater than 0 if this Date is after the Date argument.

public static void main(String[] args) throws ParseException {
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
    Date date1 = sdf.parse("2009-12-31");
    Date date2 = sdf.parse("2010-01-31");

    System.out.println(sdf.format(date1));
    System.out.println(sdf.format(date2));

    if (date1.compareTo(date2) > 0) {
        System.out.println("Date1 is after Date2");
    } else if (date1.compareTo(date2) < 0) {
        System.out.println("Date1 is before Date2");
    } else if (date1.compareTo(date2) == 0) {
        System.out.println("Date1 is equal to Date2");
    } else {
        System.out.println("How to get here?");
    }
}

Date.before(), Date.after() and Date.equals()

这是一个对用户更友好的方法去比较两个日期

public static void main(String[] args) throws ParseException {
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
    Date date1 = sdf.parse("2009-12-31");
    Date date2 = sdf.parse("2010-01-31");

    System.out.println(sdf.format(date1));
    System.out.println(sdf.format(date2));

    if (date1.after(date2)) {
        System.out.println("Date1 is after Date2");
    }

    if (date1.before(date2)) {
        System.out.println("Date1 is before Date2");
    }

    if (date1.equals(date2)) {
        System.out.println("Date1 is equal Date2");
    }
}

Calender.before(), Calender.after() and Calender.equals()

最常用的方法去比较两个日期java.util.Calendar类

public static void main(String[] args) throws ParseException {
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
    Date date1 = sdf.parse("2009-12-31");
    Date date2 = sdf.parse("2010-01-31");

    System.out.println(sdf.format(date1));
    System.out.println(sdf.format(date2));

    Calendar cal1 = Calendar.getInstance();
    Calendar cal2 = Calendar.getInstance();
    cal1.setTime(date1);
    cal2.setTime(date2);

    if(cal1.after(cal2)){
        System.out.println("Date1 is after Date2");
    }

    if(cal1.before(cal2)){
        System.out.println("Date1 is before Date2");
    }

    if(cal1.equals(cal2)){
        System.out.println("Date1 is equal Date2");
    }

}

来源：How To Compare Dates In Java