The issue of comparing the size of date type in Java program

    /**
      * Time comparison method compareTo
      * If d1 is larger than d2, the result = 1
      * If d1 is more than d2, etc. The result = 0
      * If d1 is smaller than d2, the result =-1
      *
      * @param d1
      * @param d2
      */
    private void printResultCompareTo(Date d1,Date d2){
        if((d2) == 1){
            (new SimpleDateFormat(YYYY_MM_DD_HH_MM_SS).format(d1) + " exist " + new SimpleDateFormat(YYYY_MM_DD_HH_MM_SS).format(d2) + "after");
        }else if((d2) == 0){
            (new SimpleDateFormat(YYYY_MM_DD_HH_MM_SS).format(d1) + " = " + new SimpleDateFormat(YYYY_MM_DD_HH_MM_SS).format(d2) );
        }else{
            (new SimpleDateFormat(YYYY_MM_DD_HH_MM_SS).format(d1) + " exist " + new SimpleDateFormat(YYYY_MM_DD_HH_MM_SS).format(d2) + "Before");
        }
    }

    /**
      * Compare using the before method
      *
      * @param d1
      * @param d2
      */
    private void printResultBefore(Date d1,Date d2){
        if((d2)){
            (new SimpleDateFormat(YYYY_MM_DD_HH_MM_SS).format(d1) + " exist " + new SimpleDateFormat(YYYY_MM_DD_HH_MM_SS).format(d2) + "Before");
        }else{
            (new SimpleDateFormat(YYYY_MM_DD_HH_MM_SS).format(d1) + " exist " + new SimpleDateFormat(YYYY_MM_DD_HH_MM_SS).format(d2) + "after");
        }
    }

    /**
      * Compare using after method
      *
      * @param d1
      * @param d2
      */
    private void printResultAfter(Date d1,Date d2){
        if((d2)){
            (new SimpleDateFormat(YYYY_MM_DD_HH_MM_SS).format(d1) + " exist " + new SimpleDateFormat(YYYY_MM_DD_HH_MM_SS).format(d2) + "after");
        }else{
            (new SimpleDateFormat(YYYY_MM_DD_HH_MM_SS).format(d1) + " exist " + new SimpleDateFormat(YYYY_MM_DD_HH_MM_SS).format(d2) + "Before");
        }
    }

    /**
      * Use getTime method to get millisecond values ​​comparison
      *
      * @param d1
      * @param d2
      */
    private void printResultGetTime(Date d1,Date d2){
        if(() > ()){
            (new SimpleDateFormat(YYYY_MM_DD_HH_MM_SS).format(d1) + " exist " + new SimpleDateFormat(YYYY_MM_DD_HH_MM_SS).format(d2) + "after");
        }else if(() == ()){
            (new SimpleDateFormat(YYYY_MM_DD_HH_MM_SS).format(d1) + " = " + new SimpleDateFormat(YYYY_MM_DD_HH_MM_SS).format(d2) );
        }else{
            (new SimpleDateFormat(YYYY_MM_DD_HH_MM_SS).format(d1) + " exist " + new SimpleDateFormat(YYYY_MM_DD_HH_MM_SS).format(d2) + "Before");
        }
    }

    //Define a date1String1 string    private final String date1String1 = "2018-09-01 23:23:59";
    //Define a date1String2 string    private final String date1String2 = "2020-04-20 23:23:59";
    //Define a date1String3 string    private final String date1String3 = "2021-04-20 23:23:59";
    //Parameter formatting type    private final String YYYY_MM_DD_HH_MM_SS = "yyyy-MM-dd HH:mm:ss";

    //Define date type data    private Date date1;
    private Date date2;
    private Date date3;

    @Before
    public void beforPrint() throws ParseException {
        date1 = new SimpleDateFormat(YYYY_MM_DD_HH_MM_SS).parse(date1String1);
        date2 = new SimpleDateFormat(YYYY_MM_DD_HH_MM_SS).parse(date1String2);
        date3 = new SimpleDateFormat(YYYY_MM_DD_HH_MM_SS).parse(date1String3);
        ("date1: " + date1String1);
        ("date2: " + date1String2);
        ("date3: " + date1String3);
    }

    /**
      * Compare with compareTo
      */
    @Test
    public void testCompare(){
        ("--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------);
        printResultCompareTo(date1, date2);
        printResultCompareTo(date3, date2);
        ("------------------------------------------------------------------------------------------------------------------------------);
        printResultBefore(date1,date2);
        printResultBefore(date3, date2);
        ("------------------------------------------------------------------------------------------------------------------------------);
        printResultAfter(date1, date2);
        printResultAfter(date3, date2);
        ("------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------);
        printResultGetTime(date1, date2);
        printResultGetTime(date3, date2);
    }