关于Java语言中的时间格式化

在做统计报表时，须将时间格式化为所需格式存入数据库……

package com.sgcc.kpi.rs.entity.sample;

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

import org.apache.commons.lang3.time.DateUtils;

/**
 * 向数据库插入指标信息时各种格式化时间字符串——公共类，静态调用
 * @author wu_wenqi
 * @version 2012-06-25
 */
public class Pubsysdate {
	
	private static Calendar c = Calendar.getInstance();
	
	/**
	 * 按年统计时所需系统时间
	 * @see 例如：to_date('2012-01-01 00:00:00', 'yyyy-mm-dd hh24:mi:ss')
	 */
	public static String SYSDATE_FOR_YEAR = getSysdateForYear();
	
	/**
	 * 按月统计时所需系统时间
	 * @see 例如：to_date('2012-6-01 00:00:00', 'yyyy-mm-dd hh24:mi:ss')
	 */
	public static String SYSDATE_FOR_MONTH = getSysdateForMonth();
	
	/**
	 * 按周统计
	 */
	public static String SYSDATE_FOR_WEEK = getSysdateForWeek();
	
	/**
	 * 按天统计时所需系统时间
	 * @see 例如：to_date('2012-6-25 00:00:00', 'yyyy-mm-dd hh24:mi:ss')
	 */
	public static String SYSDATE_FOR_DAY = getSysdateForDay();
	
	/**
	 * 按年统计时所需系统时间方法
	 * @return 例如：to_date('2012-01-01 00:00:00', 'yyyy-mm-dd hh24:mi:ss')
	 */
	private static String getSysdateForYear(){
		String re = "to_date('";
		re += c.get(Calendar.YEAR) - 1;
		re += "-01-01 00:00:00', 'yyyy-mm-dd hh24:mi:ss')";
		return re;
	}
	
	/**
	 * 按月统计时所需系统时间方法
	 * @return 例如：to_date('2012-6-01 00:00:00', 'yyyy-mm-dd hh24:mi:ss')
	 */
	private static String getSysdateForMonth(){
		String re = "to_date('";
		if(c.get(Calendar.MONTH) == 0){
			re += c.get(Calendar.YEAR) - 1;
			re += "-12";
		}else{
			re += c.get(Calendar.YEAR);
			re += "-";
			re += c.get(Calendar.MONTH);
		}
		re += "-01 00:00:00', 'yyyy-mm-dd hh24:mi:ss')";
//		System.out.println(re);
		return re;
	}
	
	/**
	 * 按周统计
	 * @return
	 */
	private static String getSysdateForWeek(){
		DateFormat df = DateFormat.getDateInstance();
		String re = "to_date('";
		Date datetemp = c.getTime();
		Date date = DateUtils.addWeeks(datetemp, -1);
		int temp = date.getDay();
		if(temp == 1){//周一
			date = DateUtils.addDays(date, -0);
		}else if(temp == 2){//周二
			date = DateUtils.addDays(date, -1);
		}else if(temp == 3){//周三
			date = DateUtils.addDays(date, -2);
		}else if(temp == 4){//周四
			date = DateUtils.addDays(date, -3);
		}else if(temp == 5){//周五
			date = DateUtils.addDays(date, -4);
		}else if(temp == 6){//周六
			date = DateUtils.addDays(date, -5);
		}else if(temp == 0){
			date = DateUtils.addDays(date, -6);
		}
		re += df.format(date);
		re += " 00:00:00', 'yyyy-mm-dd hh24:mi:ss')";
		return re;
	}
	
	/**
	 * 按天统计时所需系统时间
	 * @return 例如：to_date('2012-6-25 00:00:00', 'yyyy-mm-dd hh24:mi:ss')
	 */
	private static String getSysdateForDay(){
		String re = "to_date('";
		if(c.get(Calendar.DAY_OF_MONTH) == 1){
			if(c.get(Calendar.MONTH) == 0){ //一月份要返回上年的最后一天
				re += c.get(Calendar.YEAR) - 1;
				re += "-12-31";
			}else if(c.get(Calendar.MONTH) == 2){ //二月要判断是28天还是29天
				re += c.get(Calendar.YEAR);
				re += "-";
				re += c.get(Calendar.MONTH);
				re += "-" + getLastDayFor2Month(c.get(Calendar.YEAR));
			}else if(c.get(Calendar.MONTH) == 1 
					|| c.get(Calendar.MONTH) == 3 
					|| c.get(Calendar.MONTH) == 5 
					|| c.get(Calendar.MONTH) == 7 
					|| c.get(Calendar.MONTH) == 8 
					|| c.get(Calendar.MONTH) == 10 
					|| c.get(Calendar.MONTH) == 12){ //每月31天
				re += c.get(Calendar.YEAR);
				re += "-";
				re += c.get(Calendar.MONTH);
				re += "-31";
			}else{ //每月30天
				re += c.get(Calendar.YEAR);
				re += "-";
				re += c.get(Calendar.MONTH);
				re += "-30";
			}
		}else{
			re += c.get(Calendar.YEAR);
			re += "-";
			re += c.get(Calendar.MONTH) + 1;
			re += "-";
			re += c.get(Calendar.DAY_OF_MONTH) - 1;
		}
		re += " 00:00:00', 'yyyy-mm-dd hh24:mi:ss')";
		return re;
	}
	
	/**
	 * 判断当年是闰年还是平年并返回二月的最后一天
	 */
	private static int getLastDayFor2Month(int year){
		if((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0))
		{
		    return 29;
		}else{
			return 28;
		}
	}
}