Java中日期API常见问题整理

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

import org.junit.Test;

public class Time {
    //使用DataFormat以指定格式显示时间
    @Test
    public void display() {
        Date date = new Date();
        DateFormat format = new SimpleDateFormat("yyyy-MM-dd kk:mm:ss");
        String time = format.format(date);
        System.out.println("北京时间：" + time);
    }

    //时间减法，计算时间间隔
    @Test
    public void interval() {
        Date begin = new Date();
        for (int i = 0; i < Integer.MAX_VALUE; i++) {

        }
        Date end = new Date();
        long beginTime = begin.getTime();
        long endTime = end.getTime();
        System.out.println("循环历时：" + (endTime - beginTime) + "ms");
    }

    //时间加法，计算一段时间后的时刻
    @Test
    public void add() {
        DateFormat format = new SimpleDateFormat("yyyy-MM-dd kk:mm:ss");
        Date begin = new Date();
        int interval = 30;
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(begin);
        calendar.add(Calendar.MINUTE, interval);
        Date end = calendar.getTime();
        System.out.println("现在时间：" + format.format(begin));
        System.out.println(interval + "分钟后：" + format.format(end));
    }
}