Java: Date operation

DateOperation.java

import java.util.Date;
import java.text.SimpleDateFormat;
import java.sql.Timestamp;
import java.lang.StringBuffer;

public class DateOperation{

	private Date date;

	public DateOperation(){
		date = new Date();
	}

	public void printDateAsClass(){
		System.out.println(date);
	}

	public void printDateAsString(){
		SimpleDateFormat yyMMddFormat = new SimpleDateFormat("yyyy-MM-dd");
		String yyMMddString = yyMMddFormat.format(date);
		System.out.println(yyMMddString);

		SimpleDateFormat hhmmssFormat = new SimpleDateFormat("HH:mm:ss");
		String hhmmssString = hhmmssFormat.format(date);
		System.out.println(hhmmssString);

		SimpleDateFormat weekInYearFormat = new SimpleDateFormat("w");
		String weekInYearString = weekInYearFormat.format(date);
		System.out.println(weekInYearString);

	}

	public void printDateAsTimestamp(){
		Timestamp timestamp = new Timestamp(date.getTime());
		System.out.println("use java.sql.Timestamp to print as timestamp: "+timestamp.getTime());
		System.out.println("or using directly date.getTime(): "+date.getTime());
	}

	public void compareDateUsingMilliSecond(){
		Date newDate = new Date();
		long dateDifference = newDate.getTime() - date.getTime();
		if(dateDifference > 0){
			System.out.println("newDate is later...");
		}else{
			System.out.println("date is later...");
		}
		System.out.println("date difference is :"+dateDifference);
		
	}

	public void convertStringToDate(){
		String dateString = "1989-10-23 02:20:34";
		SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
		Date dateFromString = null;
		try{
			dateFromString = formatter.parse(dateString);
		}catch(Exception e){}
		System.out.println("date converted from string: "+dateFromString);
	}

	public void convertLongTimestampToDate(){
		Date newDate = new Date();
		long longTimestamp = newDate.getTime();
		longTimestamp += 10000;
		Date dateFromTimestamp = new Date(longTimestamp);
		System.out.println("date from long timestamp: "+dateFromTimestamp);
	}

	public String compareDateWithCurrentTime(Date date){
		Date currentDate = new Date();
		StringBuffer sb = new StringBuffer();
		sb.append("当前时间和目标时间比");
		long timeDiff = currentDate.getTime() - date.getTime();
		if(timeDiff > 0){
			sb.append("已过");
		}else{
			sb.append("还差");
			timeDiff = timeDiff * -1;
		}
		long dayDiff = timeDiff/(1000 * 60 * 60 * 24);
		long hourDiff = timeDiff/ (1000 * 60 * 60);
		long minuteDiff = timeDiff/(1000 * 60);
		long secondDiff = timeDiff/(1000);
		
		if(dayDiff != 0){
			sb.append(dayDiff + "天");
		}else if(hourDiff != 0){
			sb.append(hourDiff + "小时");
		}else if(minuteDiff != 0){
			sb.append(minuteDiff + "分钟");
		}else if(secondDiff != 0){
			sb.append(secondDiff+"秒");
		}else{
			sb.append(timeDiff+"毫秒");
		}
		
		return sb.toString();
	}
	

	public static void main(String args[]){
		DateOperation dateOperation = new DateOperation();
		dateOperation.printDateAsClass();
		dateOperation.printDateAsString();
		dateOperation.printDateAsTimestamp();
		dateOperation.compareDateUsingMilliSecond();
		dateOperation.convertStringToDate();
		dateOperation.convertLongTimestampToDate();

		String oldDateString = "2012-08-13";
		SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
		Date convertedDate = null;
		try{
			convertedDate = sdf.parse(oldDateString);
		}catch(Exception e){}
		System.out.println(dateOperation.compareDateWithCurrentTime(convertedDate));
	}
}