Calculate how many hours and minutes have passed since a date in Java [closed]

In his day I did a small class to add and subtract dates, you just have to get that date in milliseconds. You can use it to obtain a date that you give in the constructor to obtain the data of that date in String format, or you can instantiate the class without constructor and use the method operateCustomDate , in which operation can be 0 (to add dates) or 1 (Subtract dates) to a Date date in which you add or subtract (depending on the operation you choose) the milliseconds given in the third parameter: milliseconds . I hope it works for you

import java.time.LocalDate;
import java.time.ZoneId;
import java.util.Date;


public class DateCalculator {

public Date Date;

public String Day;
public String Month;
public int MonthValue;
public String NumberDay;
public String Year;
public String TimeZone;

public String Seconds;
public String Minutes;
public String Hours;

public DateCalculator(Date date) {

    this.Date = date;

    String DateString = date.toString();

    //System.out.println(DateString);

    String[] DateSplitted = DateString.split(" ");

    for (int i = 0; i < DateSplitted.length; i++) {
        //System.out.println(i + ". " +DateSplitted[i]);
        switch (i) {
            case 0: {
                this.Day = DateSplitted[0];
            }
            case 1: {
                this.Month = DateSplitted[1];

                LocalDate localDate = date.toInstant().atZone(ZoneId.systemDefault()).toLocalDate();
                this.MonthValue = localDate.getMonthValue();
            }
            case 2: {
                this.NumberDay = DateSplitted[2];
            }
            case 3: {
                String[] hour = DateSplitted[3].split(":");
                this.Hours = hour[0];
                this.Minutes = hour[1];
                this.Seconds = hour[2];
            }
            case 4: {
                this.TimeZone = DateSplitted[4];
            }
            case 5: {
                this.Year = DateSplitted[5];
            }
        }
    }
}

public DateCalculator() {
    /* EMPTY CONSTRUCTOR FOR USE THE CLASS WITH 
     CUSTOM VALUE CALCULATOR (operateCustomDate()) */
}

public String getDay() {
    return this.Day;
}

public String getMonth() {
    return this.Month;
}

public String getDayNumber() {
    return this.NumberDay;
}

public int getNumberMonth() {
    return this.MonthValue;
}

public String getCompleteHour() {
    String CompleteHour = this.Hours + ":" + this.Minutes + ":" + this.Seconds;

    return CompleteHour;
}

public String getCompleteDay() {
    String CompleteDay = this.Year + "-" + this.Month + "-" + this.NumberDay + " " + this.getCompleteHour();

    return CompleteDay;
}

public String getHour() {
    return this.Hours;
}

public String getMinute() {
    return this.Minutes;
}

public String getSeconds() {
    return this.Seconds;
}

public String getTimeZone() {
    return this.TimeZone;
}

public String getYear() {
    return this.Year;
}

/*

operation: 
        0: +
        1: -

Operate with the current Date

NOTE: FOR BIG LONG VALUES IN MILLISECONDS, USE 
long milliseconds = Long.parseLong(String number value);
 */

public Date operateCustomDate(int operation, Date date, long milliseconds) {
    long CurrentMs = date.getTime();

    long FinalDate;

    if (operation == 0) {
        FinalDate = CurrentMs + milliseconds;

        Date newDate = new Date(FinalDate);

        return newDate;
    } else if (operation == 1) {
        FinalDate = CurrentMs - milliseconds;

        Date newDate = new Date(FinalDate);

        return newDate;
    } 
    return null;
}
}

To be able to obtain the data from the database, being java I would use the library jdbc, from which I leave a tutorial by here , once obtained a String of the date, you can use the class SimpleDateFormat , whose documentation you can find here . This class allows you to pass the String to Date so you can do the operations you need.