Java Local Time轉GMT用法及代碼示例

// Java Program to convert local time to GMT
// Importing libraries
// 1. input output libraries
import java.io.*;
// 3. Text class
import java.text.DateFormat;
import java.text.SimpleDateFormat;
// 2. Utility libraries for
// Date and TimeZone class
import java.util.Date;
import java.util.TimeZone;
// Class
class GFG {
    // Main driver method
    public static void main(String[] args)
    {
        // Creating a Date class object
        // to take local time from the user
        Date localTime = new Date();
        // Creating a DateFormat class object to
        // convert the localtime to GMT
        DateFormat s = new SimpleDateFormat("dd/MM/yyyy"
                                            + " "
                                            + " HH:mm:ss");
        //  function will helps to get the GMT Timezone
        // using the getTimeZOne() method
        s.setTimeZone(TimeZone.getTimeZone("GMT"));
        // One can get any other time zone also
        // by passing some other argument to it
        // Printing the local time
        System.out.println("local Time:" + localTime);
        // Printing the GMT time to
        // illustrate changes in GMT time
        System.out.println("Time IN Gmt : "
                           + s.format(localTime));
    }
}

// Java Program to convert Local time to
// GMT time 
// Importing all input output classes
import java.io.*;
// Importing all time classes
import java.time.*;
// Class
class GFG {
    // Main driver method
    public static void main(String[] args)
    {
        // Instant operator helps to note
        // the time and the location of it
        // Creating an object of Instant type
        // using the now() method
        Instant now = Instant.now();
        // Now with the help of Instant operator
        // zoned operator is called
        // Creating an object of ZonedDateTime
        ZonedDateTime zdt = ZonedDateTime.ofInstant(
            now, ZoneId.systemDefault());
        // Printing the local time
        System.out.println(" Local : " + zdt);
        // Creating an object of  Instant type
        // taking any other instant method
        Instant instant = Instant.now();
        // Printing the GMT/UTC time by parsing with string
        // using the toString() method
        System.out.println(" GMT : "+instant.toString());
    }
}