How to get String , starting from 1 and ending at n?

Question

How to do that, When user inputs n=4 then it should generate a string like str="1234"?

for (int i = 1; i <= 4; i++) { string+=i; } – JYoThI Apr 29 '17 at 08:59 — JYoThI, Apr 29 '17 at 08:59

Youcef LAIDANI · Accepted Answer · 2017-04-29T09:14:15.917

5

You can use a simple loop for example :

int n = 4;
String str = "";
for (int i = 1; i <= n; i++) {
    str+=i;
}

can we directly get int= 1234

In this case you can parse it like this :

int result = Integer.parseInt(str);

If you want to avoid this and get int from the begging you can use :

int n = 4;
int result = 0;
for (int i = 1; i <= n; i++) {
    result *= 10;
    result += i;
}

edited Apr 29 '17 at 09:14

answered Apr 29 '17 at 08:58

Youcef LAIDANI

can we directly get int= 1234 – Abhishec Kumar Apr 29 '17 at 09:00
you can convert it @AbhishecKumar i will edit my answer – Youcef LAIDANI Apr 29 '17 at 09:01
check my edit @AbhishecKumar – Youcef LAIDANI Apr 29 '17 at 09:05

score 5 · Answer 2 · answered Apr 29 '17 at 08:59

5

int n = 10;
StringBuffer s = new StringBuffer();
for(int i=1;i<=n;i++){
s = s.append(i); 
}
System.out.println(s.toString());

answered Apr 29 '17 at 08:59

Rahul Rabhadiya

score 1 · Answer 3 · edited May 23 '17 at 12:02

Note: Do not use String concatenation in for, instead it use StringBuilder.

Take a look at this question.

In your case n is a small value and because it is not so important. If n has a big value it will be a vast of memory.

Java 8 way

int n = 4;

StringBuilder sb = new StringBuilder();
IntStream.rangeClosed(1, n).forEach(sb::append);
String str = sb.toString();

Java 7 way

int n = 4;

StringBuilder sb = new StringBuilder();
for (int i = 1; i <= n; i++) {
    sb.append(i);
}
String str = sb.toString();

3 Answers3