Calendar 计算日期差

package test;

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

/**
 * @description 日期比较天 月 年
 * @author www.javawind.net
 */
public class DateTest {
	public static void main(String[] args) {
		String date = "2008-06-12";

		DateTest.compareDate(date, null, 0);
		DateTest.compareDate(date, null, 1);
		DateTest.compareDate(date, null, 2);

		date = "2006-06-03";
		DateTest.compareDate(date, null, 0);
		DateTest.compareDate(date, null, 1);
		DateTest.compareDate(date, null, 2);
		DateTest.compareDate(date, "2009-06-01", 0);
		DateTest.compareDate(date, "2009-06-01", 1);
		DateTest.compareDate(date, "2009-06-01", 2);
		
		System.out.println(DateTest.getMonthNum("2015--1","2016-12-11"));
		System.out.println("dasdas");
	}

	/**
	 * @param date1
	 *            需要比较的时间 不能为空(null),需要正确的日期格式
	 * @param date2
	 *            被比较的时间 为空(null)则为当前时间
	 * @param stype
	 *            返回值类型 0为多少天，1为多少个月，2为多少年
	 * @return
	 */
	public static int compareDate(String date1, String date2, int stype) {
		int n = 0;

		String[] u = { "天", "月", "年" };
		String formatStyle = stype == 1 ? "yyyy-MM" : "yyyy-MM-dd";

		date2 = date2 == null ? DateTest.getCurrentDate() : date2;

		DateFormat df = new SimpleDateFormat(formatStyle);
		Calendar c1 = Calendar.getInstance();
		Calendar c2 = Calendar.getInstance();
		try {
			c1.setTime(df.parse(date1));
			c2.setTime(df.parse(date2));
		} catch (Exception e3) {
			System.out.println("wrong occured");
		}
		// List list = new ArrayList();
		while (!c1.after(c2)) { // 循环对比，直到相等，n 就是所要的结果
			// list.add(df.format(c1.getTime())); // 这里可以把间隔的日期存到数组中 打印出来
			n++;
			if (stype == 1) {
				c1.add(Calendar.MONTH, 1); // 比较月份，月份+1
			} else {
				c1.add(Calendar.DATE, 1); // 比较天数，日期+1
			}
		}

		n = n - 1;

		if (stype == 2) {
			n = (int) n / 365;
		}

		System.out.println(date1 + " -- " + date2 + " 相差多少" + u[stype] + ":" + n);
		return n;
	}

	/**
	 * 得到当前日期
	 * 
	 * @return
	 */
	public static String getCurrentDate() {
		Calendar c = Calendar.getInstance();
		Date date = c.getTime();
		SimpleDateFormat simple = new SimpleDateFormat("yyyy-MM-dd");
		return simple.format(date);
	}

	public static int getMonthNum(String date1, String date2) {

		String formatStyle = "yyyy-MM-dd";
		DateFormat df = new SimpleDateFormat(formatStyle);
		Calendar c1 = Calendar.getInstance();
		Calendar c2 = Calendar.getInstance();
		try {
			c1.setTime(df.parse(date1));
			c2.setTime(df.parse(date2));
		} catch (Exception e) {
			throw new RuntimeException("date parse and set exception");
		}
		
		int count = 0;
		while (!c1.after(c2)) {
			count++;
			c1.add(Calendar.MONTH, 1); // 比较月份，月份+1
		}
		return count;
	}
}