需要一个java程序,12小时和24小时制的相互转换

Date date=new Date(12/12/11 8:22:09 PM); System.out.println(Time in 24Hours =+new SimpleDateFormat(HH:mm).format(date));

根据时间的小时值，判断、转换就是了

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package com.test;import java.text.ParseException;import java.text.SimpleDateFormat;import java.util.Locale;public class AmPmUtil{ public static void main(String[] args) { try { System.out.println(AmPmUtil.convert(9:30pm)); System.out.println(AmPmUtil.convert(9:30am)); System.out.println(AmPmUtil.convert(12:30pm)); System.out.println(AmPmUtil.convert(9:30)); System.out.println(AmPmUtil.convert(19:30)); } catch (final ParseException e) { e.printStackTrace(); } } /** * 转换到24小时 * @param ampm * @return * @throws ParseException */ private static String convert(String ampm) throws ParseException { final SimpleDateFormat format = new SimpleDateFormat(HH:mm); SimpleDateFormat parse = null; if (ampm.indexOf(m) -1) { parse = new SimpleDateFormat(hh:mma, Locale.ENGLISH); } else { parse = format; } return format.format(parse.parse(ampm)); } }

SimpleDateFormat objSDateFormat = new SimpleDateFormat(yyyy-MM-dd HH:mm:ss);
String strCurrentTime = objSDateFormat.format(Date类型的时间);

注：大写的HH为24小时制，小写的hh为12小时制，当然还可以在ss的后面加上 a，这样可以在后面显示上下文：显示效果为“2008-03-24 17:00:14 下午”

这个更全
实现思路就是输入一个时间，之后会输出相应的12小时和24小时效果展示：
import java.text.SimpleDateFormat;
import java.util.Locale;
import java.util.Scanner;

public class App {

public static void main(String[] args) {
while (true) {
System.out.println(Enter time in 24-hour notation:);
Scanner sc = new Scanner(System.in);
String line = sc.nextLine();
try {
outTime(line);
} catch (TimeFormatException e) {
System.out.println(There is no such time as + line);
System.out.println(Try again:);
continue;
}
sc = new Scanner(System.in);
line = sc.nextLine();
if (n.equalsIgnoreCase(line)) {
break;
}

}
System.out.println(End of program);
}

public static void outTime(String line) throws TimeFormatException {
SimpleDateFormat _24time = new SimpleDateFormat(HH:mm);
SimpleDateFormat _12time = new SimpleDateFormat(hh:mm a,
Locale.ENGLISH);
try {
String[] array = line.split(:);
if (Integer.parseInt(array[0]) 0
|| Integer.parseInt(array[0]) 23) {
throw new TimeFormatException();
}
if (Integer.parseInt(array[1]) 0
|| Integer.parseInt(array[1]) 59) {
throw new TimeFormatException();
}
System.out.println(_12time.format(_24time.parse(line)));
System.out.println(Again?(y/n));
} catch (Exception e) {
throw new TimeFormatException();
}
}
}
class TimeFormatException extends Exception {

}

import java.util.GregorianCalendar;

GregorianCalendar g = new GregorianCalendar();
System.out.print(g.getTime())//当前时间点