java.util.Calendar before()方法

java.util.Calendar.before(Object when) 是java.util包的Calendar类中的方法。如果此Calendar表示的时间早于when对象表示的时间，则该方法返回true。如果不是这种情况，则返回false。

1 语法

public boolean before(Object when)  

2 参数

when：when是要比较的对象。

3 返回值

此方法返回true或false值

4 示例1 

package com.yiidian;

/**
 * 一点教程网： http://www.yiidian.com
 */
/**
 * java.util.Calendar before()方法的例子
 */
import java.util.Calendar;  
import java.util.Date;  
public class CalendarbeforeExample1 {  
         public static void main(String[] args) {  
   // create calendar objects.  
       Calendar cal = (Calendar) Calendar.getInstance();  
      Calendar past = (Calendar) Calendar.getInstance();  
      // print the current date  
      System.out.println("Current date: " + cal.getTime());  
      // change year in future calendar  
      past.set(Calendar.YEAR, 2015);  
      System.out.println("Year is " + past.get(Calendar.YEAR));  
      // check if calendar date is after current date  
      Date time = past.getTime();  
           if (past.before(cal)) {  
         System.out.println("Date " + time + " is before current date.");  
      }  
   }  
}

输出结果为：

Current date: Mon Jul 30 04:08:30 PDT 2018
Year is 2015
Date Thu Jul 30 04:08:30 PDT 2015 is before current date.

5 示例2

package com.yiidian;

/**
 * 一点教程网： http://www.yiidian.com
 */
/**
 * java.util.Calendar before()方法的例子
 */
import java.util.Calendar;  
import java.util.Date;  
public class CalendarbeforeExample2 {     
public static void main(String[] args) {    
     // create calendar objects.  
       Calendar cal = (Calendar) Calendar.getInstance();  
     Calendar cal2 = (Calendar) Calendar.getInstance();  
      // print the current date  
      System.out.println("Current date: " + cal.getTime());  
      // change year in future calendar  
      cal2.set(Calendar.MONTH, 4);  
      System.out.println("Year is " + cal2.get(Calendar.MONTH));  
      // check if calendar date is after current date  
      Date time = cal2.getTime();       
      if (cal2.before(cal)) {  
         System.out.println("Date " + time + " is before current date.");  
      }  
   }  
}  

输出结果为：

Current date: Mon Jul 30 04:13:04 PDT 2018
Year is 4
Date Wed May 30 04:13:04 PDT 2018 is before current date.

6 示例3

package com.yiidian;

/**
 * 一点教程网： http://www.yiidian.com
 */
/**
 * java.util.Calendar before()方法的例子
 */
import java.util.Calendar;  
import java.util.Date;  
public class CalendarbeforeExample3 {  
public static void main(String[] args) {  
      // create calendar objects.  
       Calendar cal = (Calendar) Calendar.getInstance();  
      Calendar cal3 = (Calendar) Calendar.getInstance();  
      // print the current date  
      System.out.println("Current date: " + cal.getTime());  
      // change year in future calendar  
      cal3.set(Calendar.DAY_OF_MONTH, 23);  
      System.out.println("Year is " + cal3.get(Calendar.DAY_OF_MONTH));  
      // check if calendar date is after current date  
      Date time = cal3.getTime();  
      if (cal3.before(cal)) {  
         System.out.println("Date " + time + " is before current date.");  
      }     
  }     
 }  

输出结果为：

Current date: Mon Jul 30 06:19:04 PDT 2018
Year is 23
Date Mon Jul 23 06:19:04 PDT 2018 is before current date.

7 示例4

package com.yiidian;

/**
 * 一点教程网： http://www.yiidian.com
 */
/**
 * java.util.Calendar before()方法的例子
 */
import java.util.Calendar;  
import java.util.Date;  
public class CalendarbeforeExample4 {      
public static void main(String[] args) {     
      // create calendar objects.  
       Calendar cal = (Calendar) Calendar.getInstance();  
      Calendar cal3 = (Calendar) Calendar.getInstance();  
      // print the current date  
      System.out.println("Current date: " + cal.getTime());  
      // change year in future calendar  
      cal3.set(Calendar.HOUR, 30);  
      System.out.println("Now date is  " + cal3.getTime());  
       cal3.set(Calendar.MINUTE, 60);  
      System.out.println("Now date is  " + cal3.getTime());    
       cal3.set(Calendar.SECOND, 30);  
      System.out.println("Now date is  " + cal3.getTime());      
      // check if calendar date is after current date  
      Date time = cal3.getTime();       
      if (cal3.before(cal)) {  
         System.out.println("Date " + time + " is after current date.");  
      }  
}  
}

输出结果为：

Current date: Mon Jul 30 06:23:37 PDT 2018
Now date is  Tue Jul 31 06:23:37 PDT 2018
Now date is  Tue Jul 31 07:00:37 PDT 2018
Now date is  Tue Jul 31 07:00:30 PDT 2018