Java 中将毫秒转换为日期

2025年7月7日 | 阅读 3 分钟

在 Java 中，通常我们需要将毫秒转换为不同格式的日期，例如 dd MMM yyyy 和 dd MMM yyyy HH:mm:ss:SSS Z 等。

Date 是 Java 中处理日期最重要的类之一。它在内部以毫秒为单位存储日期。通过使用 Date 类的构造函数，我们可以从毫秒创建 Date 对象。

在继续之前，需要了解 SimpleDateFormat 类。它是我们用来格式化和解析数据的类之一。它帮助我们将日期从一种格式转换为另一种格式。它还有助于将字符串格式的日期转换为日期对象。简单来说，SimpleDateFormat 类用于相应地修改日期。

让我们通过一些示例来了解如何将毫秒转换为日期。

MillisecondsToDateExample1.java

// import required classes and packages  
package javaTpoint.javacodes; 
import java.text.DateFormat; 
import java.text.SimpleDateFormat; 
import java.util.Date; 
import java.util.Scanner; 
// create MillisecondsToDateExample1 class to convert milliseconds into Date 
public class MillisecondsToDateExample1 { 
// main() method start 
public static void main(String args[]) 
{ 
	// declaration of a variable for milliseconds 
		long miliSec; 
		// create scanner class object 
	Scanner sc = new Scanner(System.in);   
        		System.out.print("Enter milliseconds: ");   
        		// take input from user and initialize variable  
       		 miliSec = sc.nextLong();   
        		// close scanner class obj 
       		 sc.close(); 
       		 // create an instance of the SimpleDateFormat class for modifying the date object 
       		 DateFormat obj = new SimpleDateFormat("dd MMM yyyy HH:mm:ss:SSS Z"); 
        		// we create instance of the Date and pass milliseconds to the constructor  
        		Date res = new Date(miliSec); 
        		// now we format the res by using SimpleDateFormat 
        		System.out.println(obj.format(res)); 
} 
} 

输出

MillisecondsToDateExample2.java

// import required classes and package 
package javaTpoint.javacodes; 
import java.text.DateFormat; 
import java.text.SimpleDateFormat; 
import java.util.Calendar; 
import java.util.Date; 
//create MillisecondsToDateExample2 class to convert milliseconds into Date 
public class MillisecondsToDateExample2 { 
// main() method start 
    public static void main(String args[]) { 
       //use currentTimeMillis() method of system to get current time in milliseconds 
       long milliSec = System.currentTimeMillis(); 
       //convert milliseconds into Date by creating an object of the date class and passing milliseconds to the constructor 
       Date res = new Date(milliSec); 
       //printing value of Date(default format) 
       System.out.println("After converting milliseconds into date: " + res); 
       // create an instance of the SimpleDateFormat class for modifying date object into dd:MM:yy:HH:mm:ss and dd MMM yyyy HH:mm:ss:SSS Z format 
       DateFormat sdf1 = new SimpleDateFormat("dd:MM:yy:HH:mm:ss"); 
       DateFormat sdf2 = new SimpleDateFormat("dd MMM yyyy HH:mm:ss:SSS Z"); 
       //after formatting the res into dd:MM:yy:HH:mm:ss and dd MMM yyyy HH:mm:ss:SSS Z format 
       System.out.println("Date in dd:MM:yy:HH:mm:ss: " + sdf1.format(res)); 
       System.out.println("Date in dd MMM yyyy HH:mm:ss:SSS Z: " + sdf2.format(res)); 
       //convert milliseconds into Date by using calendar class 
       // create instance of the Calendar class 
       Calendar calndr = Calendar.getInstance(); 
       // use setTimeInMillis() method od the calendar class to set time  
       calndr.setTimeInMillis(milliSec); 
       // after formatting the date into dd:MM:yy:HH:mm:ss 
       System.out.println("After converting milliseconds into date using Calendar class: "+ sdf1.format(calndr.getTime())); 
       //copying data of one date into another one 
       Date currentdate = new Date(); 
       Date tempDate = new Date(currentdate.getTime()); 
       System.out.println("original Date: " + sdf1.format(currentdate)); 
       System.out.println("copied Date: " + sdf1.format(tempDate)); 
    } 
} 

输出