Tips in String concatenation in Java 1.6 with multiple integers

Question

I have a class which has 3 int variables named: day, month and year. I also have a method called toString() that would take the three fields and return in the format "dd/mm/yyyy" (there is no need to put 0 if the day or month has only 1 number in it).

What is the best way to do this?

public String toString(){
        String dateString = this.day + "/" + this.month + "/" + this.year;
        return dateString;
    }

OR

public String toString(){
        String dateString = Integer.toString(this.day) + "/" + Integer.toString(this.month) + "/" + Integer.toString(this.year);
        return dateString;
    }

And what about String.format("%d/%d/%d", day, month, year) ? You can even add leading zero in the format if you need. — AxelH
– AxelH, Commented May 9, 2018 at 6:05

AxelH · Accepted Answer · 2018-05-09 06:14:07Z

6

As an alternative, I would use String.format to create that String

return String.format("%d/%d/%d", day, month, year)

You want to format your date with leading zero ? Easy with the formatter :

return String.format("%02d/%02d/%02d", day, month, year)

- 0 - use leading zero instead of spaces.
- 2d - Minimum two character to print (so "2" will use " 2")

You can find the complete documentation about the flags allowed in Formatter

A simple example :

String.format("%002d", 5);

005

And an example with the date,

String.format("%02d/%02d/%02d", 9, 5, 18);

09/05/18

edited May 9, 2018 at 6:14

answered May 9, 2018 at 6:07

AxelH

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Comments

sam · Accepted Answer · 2018-05-09 06:17:47Z

3

You may also write that in a single statement. There's no need to typecast Integer to String explicitly unless you're not sure that day, month and year are integers i.e. int, or you want to do an explicit exception handling.

@Override
public String toString() {
    return (this.day + "/" + this.month + "/" + this.year);
}

edited May 9, 2018 at 6:17

sam

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answered May 9, 2018 at 6:05

Abhishek

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Comments

Darpan Sanghavi · Accepted Answer · 2018-05-09 06:09:50Z

2

First one with out any doubt, in the second one you are converting Integer to String explicitly and then again concatenating in String while returning which does not make much sense.

edited May 9, 2018 at 6:09

answered May 9, 2018 at 6:02

Darpan Sanghavi

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3 Comments

Huy Anh Dinh Over a year ago

you meant converting integers into string and then concatenate?

Darpan Sanghavi Over a year ago

Yes. Concatenating converts them to string only.

Kayaman Over a year ago

It's not converting a String to Integer first. Integer.toString() converts an int to a String. However it's still unnecessary.

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