java 原生类时间处理

java获取当前时间前一周、前一月、前一年的时间

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

     public static void sampleJDK() {
		// 1 创建一个任意时间对象 , 如： 2012-12-14 15:23:55
		Calendar calendar = Calendar.getInstance();
		calendar.set(2012, Calendar.NOVEMBER, 15, 18, 23, 55);

		// 2 计算任意两个时间之间相差的天数
		Calendar start = Calendar.getInstance();
		start.set(2012, Calendar.NOVEMBER, 20);

		Calendar end = Calendar.getInstance();
		end.set(2012, Calendar.NOVEMBER, 12);

		long startTim = start.getTimeInMillis(); // 毫秒
		long endTim = end.getTimeInMillis();// 毫秒
		long diff = endTim - startTim;
		int diff_days = (int) (diff / 1000 / 60 / 60 / 24);
		System.out.println(\"相差天数：\" + diff_days);

		// 获取 18 天之后的某天在下个月的当前周的第一 天日期
		Calendar current = Calendar.getInstance();
		DateFormat dataFormat = new SimpleDateFormat(\"yyyy-MM-dd HH:mm:ss\");
		System.out.println(dataFormat.format(current.getTime()));

		current.add(Calendar.DAY_OF_MONTH, 18);
		current.add(Calendar.MONTH, 1);
		System.out.println(dataFormat.format(current.getTime()));
		
		SimpleDateFormat format = new SimpleDateFormat(\"yyyy-MM-dd HH:mm:ss\");
        Calendar c = Calendar.getInstance();
         
        //过去七天
        c.setTime(new Date());
        c.add(Calendar.DATE, - 7);
        Date d = c.getTime();
        String day = format.format(d);
        System.out.println(\"过去七天：\"+day);
         
        //过去一月
        c.setTime(new Date());
        c.add(Calendar.MONTH, -1);
        Date m = c.getTime();
        String mon = format.format(m);
        System.out.println(\"过去一个月：\"+mon);
         
        //过去三个月
        c.setTime(new Date());
        c.add(Calendar.MONTH, -3);
        Date m3 = c.getTime();
        String mon3 = format.format(m3);
        System.out.println(\"过去三个月：\"+mon3);
         
        //过去一年
        c.setTime(new Date());
        c.add(Calendar.YEAR, -1);
        Date y = c.getTime();
        String year = format.format(y);
        System.out.println(\"过去一年：\"+year);

	}