Java 日历 before()方法

java.util.Calendar.before()是java.util包中 Calendar 类的一个方法。如果这个Calendar所代表的时间在 when Object所代表的时间之前，该方法返回true。如果不是这种情况，则返回false。

语法:

public boolean before(Object when)Where, **when** is the Object that is to be compared.

下面是一些例子，以更好地理解Calendar.before()函数的实现。

例子1 :

// Implementation to show the usage// of before(Object when) method of// Calendar classimport java.util.*;  class GFG {      public static void main(String[] args)        throws InterruptedException    {          // creating calendar object        Calendar cal_obj1 = Calendar.getInstance();          // printing current date        System.out.println("Time 1 : " + cal_obj1.getTime());          // sleep for 3 seconds        Thread.sleep(3000);          // creating Calendar object        Calendar cal_obj2 = Calendar.getInstance();          // printing current date        System.out.println("Time 2 : " + cal_obj2.getTime());          // checking if 1st date is before 2nd date        // and printing the result        System.out.println(cal_obj1.before(cal_obj2));    }}

输出:

Time 1 : Wed Feb 28 15:43:19 IST 2018Time 2 : Wed Feb 28 15:43:22 IST 2018true

例2 :

// Implementation to show the usage// of before(Object when) method of// Calendar classimport java.util.*;  class GFG {      public static void main(String[] args)    {          // creating calendar objects        Calendar cal_obj1 = Calendar.getInstance();        Calendar cal_obj2 = Calendar.getInstance();          // displaying the current date        System.out.println("Current date is : " + cal_obj1.getTime());          // changing year in cal_obj2 calendar        cal_obj2.set(Calendar.YEAR, 2010);          // displaying the year        System.out.println("Year is " + cal_obj2.get(Calendar.YEAR));          // check if calendar date is before current date        System.out.println("Result : " + cal_obj1.before(cal_obj2));    }}

输出:

Current date is : Wed Feb 28 15:50:16 IST 2018Year is 2010Result : false

例3 :

// Implementation to show the usage// of before(Object when) method of// Calendar classimport java.util.*;  class GFG {      public static void main(String[] args)    {          // creating calendar objects        Calendar cal_obj1 = Calendar.getInstance();        Calendar cal_obj2 = Calendar.getInstance();          // displaying the current date        System.out.println("Current date is : " + cal_obj1.getTime());          // changing year in cal_obj2 calendar        cal_obj2.set(Calendar.YEAR, 2025);          // displaying the year        System.out.println("Year is " + cal_obj2.get(Calendar.YEAR));          // check if calendar date is before current date        System.out.println("Result : " + cal_obj1.before(cal_obj2));    }}

输出:

Current date is : Wed Feb 28 16:15:55 IST 2018Year is 2025Result : true