日期计算与格式化

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

public class DateUtil {

    public static final int SECONDE=1000;
    public static final int MINUTE=SECONDE* 60;
    public static final int HOUR=MINUTE * 60;
    public static final int DAY=HOUR * 24;

    public final static String DATE_FORMATE = "MM/dd/yyyy";
    public final static String DATETIME_FORMATE = DATE_FORMATE + " HH:mm";
    
    private static Calendar c=Calendar.getInstance();

    private DateUtil(){
        //nothing
    }

    public static Date buildDate(int year,int month,int day){
        c.set(Calendar.YEAR,year);
        c.set(Calendar.MONTH,month);
        c.set(Calendar.DAY_OF_MONTH,day);
        c.set(Calendar.HOUR,0);
        c.set(Calendar.MINUTE,0);
        c.set(Calendar.SECOND,0);
        c.set(Calendar.MILLISECOND,0);
        return c.getTime();
    }

    public static Date buildDate(int month,int day){
        c.set(Calendar.MONTH,month);
        c.set(Calendar.DAY_OF_MONTH,day);
        c.set(Calendar.HOUR,0);
        c.set(Calendar.MINUTE,0);
        c.set(Calendar.SECOND,0);
        c.set(Calendar.MILLISECOND,0);
        return c.getTime();
    }
    //给定日期(date)与天数(day)，计算出从date开始day天后的日期
    public static Date afterDays(Date someday,int days){
        c.setTimeInMillis(someday.getTime()+DAY*days);
        return c.getTime();
    }

    public static Date beforeDays(Date someday,int days){
        return afterDays(someday,-days);
    }
    //明天
    public static Date tomorrow(){
        return afterDays(new Date(),1);
    }
    //昨天
    public static Date yestoday(){
        return beforeDays(new Date(),1);
    }

    public static Date parseDate(String str,String format,Date defaultValue) {
        SimpleDateFormat sdf = new SimpleDateFormat(format);
        Date result;
        try {
            result=sdf.parse(str);
        } catch (ParseException e) {
            return defaultValue;
        } catch (IllegalArgumentException iae) {
            return defaultValue;
        }
        
        return result;
    }
   
    public static Date parseDate(String str,Date defaultValue) {
        return parseDate(str, DATETIME_FORMATE,defaultValue);
    }
    //解析日期
    public static Date parseDate(String str,String format) throws ParseException {
        SimpleDateFormat sdf = new SimpleDateFormat(format);
        return sdf.parse(str);
    }

    public static Date parseDate(String str) throws ParseException {
        return parseDate(str,DATETIME_FORMATE);
    }
    //格式化日期格式
    public static String format(Date d,String format){
        SimpleDateFormat sdf = new SimpleDateFormat(format);
        return sdf.format(d);
    }

    public static String format(Date d){
        return format(d,DATETIME_FORMATE);
    }

    public static String format(String format){
        return format(new Date(),format);
    }

    public static String format(){
        return format(new Date());
    }

    public static void main(String[] args) {
        System.out.println(DateUtil.buildDate(2007,5,16));
        System.out.println(DateUtil.buildDate(5,16));
        System.out.println(DateUtil.tomorrow());
        System.out.println(DateUtil.yestoday());
        System.out.println(DateUtil.format());
    }

    
}

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