Which class and variable to choose?

[kian_hong2000]

Say now i want to key in an input of 950, which class should i refer to so that i can convert it to 21:50 time?

Should the input variable be declared as string or integer would be more suitable?

[Eranga]

Since you have to do a separation, better to deal with strings according to your requirements. But in later, if you rally want to deal with the Data format, you should convert it to Date/Time format too.

[hardwired]

import java.util.*;
import java.text.*;

public class Test {
    public static void main(String[] args) {
        DateFormat format = new SimpleDateFormat("HH:mm dd MMM yyyy");
        DateFormat timeFormat = new SimpleDateFormat("HH:mm");
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(new Date());
        Date now = calendar.getTime();
        System.out.printf("now = %s%n", format.format(now));
        // Set the time for 2150.
        int year = calendar.get(Calendar.YEAR);
        int month = calendar.get(Calendar.MONTH);
        int day = calendar.get(Calendar.DAY_OF_MONTH);
        calendar.set(year, month, day, 21, 50);
        System.out.printf("setTime = %s  time = %s%n",
                           format.format(calendar.getTime()),
                           timeFormat.format(calendar.getTime()));
    }
}

[kian_hong2000]

1)
How you get the SimpleDateFormat() constructor? I thought have to follow the name of the class which is DataFormat() when declaring?


2)
There is no Date() method in the Calendar Class. How you get it?

My Java concept of OO is still new. Thanks!

[Eranga]

1)
How you get the SimpleDateFormat() constructor? I thought have to follow the name of the class which is DataFormat() when declaring?

SimpleDateFormat() constructor define from the SimpleDateFormat class. There are four overloaded constructors available. Read the doc.

2)
There is no Date() method in the Calendar Class. How you get it?

My Java concept of OO is still new. Thanks!

Again, Date() is not a method, technically. That is the default constructor of the Date class.

[hardwired]

1)How you get the SimpleDateFormat() constructor? I thought have to follow the name of the class which is DataFormat() when declaring?
Generally, yes, but DateFormat is an interface, not a class. It is implemented by the SimpleDateFormat class.

2)There is no Date() method in the Calendar Class.
Agreed.

How you get it?
The setTime method of the Calendar class takes a Date argument.
To understand these things we look at the javadocs. Being able to find your way around the docs is a key to writing java code.
Start with the Overview, look up the class/interface in the left frame, click on the link and the class api loads into the main frame. Now you can see what constructors, fields and methods are available to/in the class. Some may be inherited from superclasses.

[kian_hong2000]

How you know DataFormat is an interface not class?
But from the API, i am only able to find it as class not interface.


java.text
Class DateFormat

java.lang.Object
extended by java.text.Format
extended by java.text.DateFormat

All Implemented Interfaces:
Serializable, Cloneable

Direct Known Subclasses:
SimpleDateFormat

[Fubarable]

How you know DataFormat is an interface not class?
But from the API, i am only able to find it as class not interface.

You are actually correct and hardwired is wrong here (almost). If you at the first line of the API, it says:

public abstract class DateFormat

. So DateFormat is a class, but an abstract one, and as such it cannot be directly constructed itself but instead needs to be subclassed to be instantiated.

[hardwired]

How you know DataFormat is an interface not class?
But from the API, i am only able to find it as class not interface.
My error. Sorry.