package com.slk.utils;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.HashMap;
import java.util.Map;
/**
 * 該模組可實現自動計算當前日期對應的周，月，年的第一天與最後一天日期，並且可直接指定當前日期為任意日期。
 * 
 * @author Administrator
 * 
 */
public class DateTerminator {
	// 獲取當前日期所在周的上下界
	public final static int CURRENT_WEEK = 0;
	// 獲取當前日期上一週的上下界
	public final static int LAST_WEEK = 1;
	// 獲取當前日期所在月的上下界
	public final static int CURRENT_MONTH = 2;
	// 獲取當前日期上一月的上下界
	public final static int LAST_MONTH = 3;
	// 獲取當前日期所在月的上下界
	public final static int CURRENT_YEAR = 4;
	// 獲取當前日期上一月的上下界
	public final static int LAST_YEAR = 5;

	/**
	 * 根據日期計算所在周的上下界
	 * 
	 * @param time
	 */
	public static Map<String, Object> convertWeekByDate(Date time) {
		Map<String, Object> map = new HashMap<String, Object>();
		SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd"); // 設定時間格式
		Calendar cal = Calendar.getInstance();
		cal.setTime(time);
		// 判斷要計算的日期是否是週日，如果是則減一天計算週六的，否則會出問題，計算到下一週去了
		int dayWeek = cal.get(Calendar.DAY_OF_WEEK);// 獲得當前日期是一個星期的第幾天
		if (1 == dayWeek) {
			cal.add(Calendar.DAY_OF_MONTH, -1);
		}
		System.out.println("要計算日期為:" + sdf.format(cal.getTime())); // 輸出要計算日期
		cal.setFirstDayOfWeek(Calendar.MONDAY);// 設定一個星期的第一天，按中國的習慣一個星期的第一天是星期一
		int day = cal.get(Calendar.DAY_OF_WEEK);// 獲得當前日期是一個星期的第幾天
		cal.add(Calendar.DATE, cal.getFirstDayOfWeek() - day);// 根據日曆的規則，給當前日期減去星期幾與一個星期第一天的差值
		String imptimeBegin = sdf.format(cal.getTime());
		// System.out.println("所在周星期一的日期：" + imptimeBegin);
		cal.add(Calendar.DATE, 6);
		String imptimeEnd = sdf.format(cal.getTime());
		// System.out.println("所在周星期日的日期：" + imptimeEnd);

		map.put("first", imptimeBegin);

		map.put("last", imptimeEnd);

		return map;
	}

	/**
	 * 根據日期計算當月的第一天與最後一天
	 * 
	 * @param time
	 * @return
	 */
	public static Map<String, Object> convertMonthByDate(Date date) {
		Map<String, Object> map = new HashMap<String, Object>();
		SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
		Calendar calendar = Calendar.getInstance();
		calendar.setTime(date);
		calendar.add(Calendar.MONTH, -1);
		Date theDate = calendar.getTime();
		// 上個月第一天
		GregorianCalendar gcLast = (GregorianCalendar) Calendar.getInstance();
		gcLast.setTime(theDate);
		gcLast.set(Calendar.DAY_OF_MONTH, 1);
		String day_first = df.format(gcLast.getTime());
		// 上個月最後一天
		calendar.add(Calendar.MONTH, 1); // 加一個月
		calendar.set(Calendar.DATE, 1); // 設定為該月第一天
		calendar.add(Calendar.DATE, -1); // 再減一天即為上個月最後一天
		String day_last = df.format(calendar.getTime());
		map.put("first", day_first);
		map.put("last", day_last);
		return map;

	}

	/**
	 * 根據日期計算當年的第一天與最後一天
	 * 
	 * @param time
	 * @return
	 */
	public static Map<String, Object> convertYearByDate(Date date) {
		Map<String, Object> map = new HashMap<String, Object>();
		SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
		Calendar calendar = Calendar.getInstance();
		int year = date.getYear() + 1900;
		calendar.clear();
		calendar.set(Calendar.YEAR, year);
		Date currYearFirst = calendar.getTime();
		calendar.set(Calendar.YEAR, year + 1);
		calendar.add(calendar.DATE, -1);
		Date lastYearFirst = calendar.getTime();
		map.put("first", sdf.format(currYearFirst));
		map.put("last", sdf.format(lastYearFirst));
		return map;

	}

	/**
	 * 外部呼叫函式入口###############################################################
	 * 
	 * @param index
	 * @return
	 * @throws ParseException
	 */
	public static Map<String, Object> getDateTime(int index)
			throws ParseException {
		Map<String, Object> map = null;
		switch (index) {
		case 0:
			map = DateTerminator.convertWeekByDate(new Date());
			break;
		case 1:
			Calendar c = Calendar.getInstance();
			c.add(c.DATE, -7);
			map = DateTerminator.convertWeekByDate(c.getTime());
			break;
		case 2:
			Calendar c2 = Calendar.getInstance();
			c2.add(c2.MONTH, 1);
			map = DateTerminator.convertMonthByDate(c2.getTime());
			break;
		case 3:
			map = DateTerminator.convertMonthByDate(new Date());
			break;
		case 4:
			map = DateTerminator.convertYearByDate(new Date());
			break;
		case 5:
			Calendar c5 = Calendar.getInstance();
			c5.add(c5.YEAR, -1);
			map = DateTerminator.convertYearByDate(c5.getTime());
			break;
		default:
			break;
		}
		return map;
	}
}
 

<strong><span style="font-size:32px;">呼叫：</span></strong>

                Map<String, Object> map = null;
		//呼叫getDateTime方法預設時間為當前時間
		map = DateTerminator.getDateTime(DateTerminator.CURRENT_WEEK);
		map = DateTerminator.getDateTime(DateTerminator.LAST_WEEK);
		//map = DateTerminator.getDateTime(DateTerminator.CURRENT_MONTH);
		//map = DateTerminator.getDateTime(DateTerminator.LAST_MONTH);
		//map = DateTerminator.getDateTime(DateTerminator.CURRENT_YEAR);
		//map = DateTerminator.getDateTime(DateTerminator.LAST_YEAR);
		//輸出日期段上下界
		System.out.println(map.get("first"));
		System.out.println(map.get("last"));
		//也可指定任意時間
		SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
		map = DateTerminator.convertMonthByDate(sdf.parse("2015-06-22"));
		System.out.println(map.get("first"));
		System.out.println(map.get("last"));