Java Date compareTo()用法及代码示例

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函数：

// 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 2019
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 2019
Date 2: null
Passing null as parameter: 
Exception: java.lang.NullPointerException

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注：本文由纯净天空筛选整理自Twinkl Bajaj大神的英文原创作品 Date compareTo() method in Java with examples。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。