Java中实现24小时制时间处理与格式化的方法及示例

import java.time.LocalTime;
import java.time.format.DateTimeFormatter;

public class Main {
public static void main(String[] args) {

// 创建一个LocalTime对象表示当前系统时间为24小时制，默认就是24小时制
LocalTime currentTime = LocalTime.now();

System.out.println("Current time in 24-hour format is : " + currentTime);

// 自定义格式化输出：HH代表24小时制小时数
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("hh:mm:ss a");
String formattedTime = currentTime.format(formatter);

// 注意这里formatter虽然设置了12小时模式（"hh"），但由于currentTime是24小时制，
// 所以依然会按照0-23范围正确显示小时部分。
System.out.println("Formatted current time (even though 'h' used for hour): " + formattedTime);

// 如果你需要严格地按24小时格式输出：
DateTimeFormatter twentyFourHourFormat = DateTimeFormatter.ISO_LOCAL_TIME;
String strictlyTwentyfourFormatedTime = currentTime.format(twentyFourHourFormat);
System.out.println("Strictly Formatted Time in the ISO local time standard(24 hours): "
+ strictlyTwentyfourFormatedTime);
}
}

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

public class Main {

public static void main(String[] args) throws Exception{

Calendar calendar = Calendar.getInstance();
Date currentDate = new Date(); // 获取当前时间

// 设置calendar为24小时制
calendar.setTime(currentDate);
SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss");
sdf.setTimeZone(calendar.getTimeZone());

String CurrentTimeIn24Hoursformat = sdf.format(currentDate);
System.out.println("The current time in 24-hours system: "+ CurrentTimeIn24Hoursformat);

}
}