How to generate 4 digit random numbers in java from 0000 to 9999

Question

I tried the following

int number = ThreadLocalRandom.current().nextInt(1000, 9999 + 1);

But it won't generate 4 digit numbers like 0004,0035 and so on...

I searched for similar questions but none solved, they were different from what I need, if there's already an existing question please let me know.

I need no genarate numbers like 1485 and 0180, not only numbers starting with 0.

What's the difference between 0004 and 4 as a number? You probably want to have strings. — Henry, Jan 11 '18 at 15:28
`1000` is bigger than `1` and you specify the range as 1000-9999 — XtremeBaumer, Jan 11 '18 at 15:30

tuxdna · Accepted Answer · 2018-01-11T15:59:32.530

2

This should work:

    Random r = new Random();
    String randomNumber = String.format("%04d", r.nextInt(1001));
    System.out.println(randomNumber);

EDIT1

    Random r = new Random();
    String randomNumber = String.format("%04d", Integer.valueOf(r.nextInt(1001)));
    System.out.println(randomNumber);

EDIT2

    Random r = new Random();
    String randomNumber = String.format("%04d", (Object) Integer.valueOf(r.nextInt(1001)));
    System.out.println(randomNumber);

All three versions should work.

edited Jan 11 '18 at 15:59

answered Jan 11 '18 at 15:45

tuxdna

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The method format(String, Object[]) in the type String is not applicable for the arguments (String, int) – Goun2 Jan 11 '18 at 15:50
@hjx Updated. Use boxed Integer. Besides, both versions work for me. – tuxdna Jan 11 '18 at 15:52
unfortunately It didn't work too, are you importing something ? – Goun2 Jan 11 '18 at 15:55
the problem is with my ide, I tried in an online ide and it worked. – Goun2 Jan 11 '18 at 15:58
What Java version is it picking up ? – tuxdna Jan 11 '18 at 15:59
1.8.0 java......... – Goun2 Jan 11 '18 at 16:01
Check this question for explanation - https://stackoverflow.com/questions/30440073/how-to-use-string-format-in-java-8 – tuxdna Jan 11 '18 at 16:03
It's not generating numbers like 1485, I expected it to generate both 0001 and 1000 – Goun2 Jan 11 '18 at 16:15
`1485` is out of the range `[0000 to 1000]`. You may want to update your question with desired range. – tuxdna Jan 11 '18 at 16:18
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String randomNumber = String.format("%04d", Integer.valueOf(r.nextInt(9999))); would work ? – Goun2 Jan 11 '18 at 16:20
it worked, thanks for the help. – Goun2 Jan 11 '18 at 16:25

score 1 · Answer 2 · answered Jan 11 '18 at 15:33

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The integer values you generate will be correct for what you need. If you want to always have four characters, you can simply write the value to a String with leading zeros, like so;

String.format("%04d", number);

answered Jan 11 '18 at 15:33

Badgerman

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my ide says that number must be of type Object. – Goun2 Jan 11 '18 at 15:38
Which IDE do you use? Auto boxing is available since quite some time now. – Henry Jan 11 '18 at 15:55
@henry eclipse.. the problem is with my ide, I tried in an online ide and it worked. – Goun2 Jan 11 '18 at 15:56

How to generate 4 digit random numbers in java from 0000 to 9999

2 Answers2