returning a String with X repeated characters without a loop

Question

I stuck a little. I have a method, which should return a new String contains X times repeated character "y". X and Y are arguments of method. So, simple solution wiil be like this:

public String someMethod(int x,char y){
    String result="";
    for (int i=0;i<x;i++) result+=y;
    return result;    
}

And I've tried to figure out, is there any way to do the same just in one line, without looping. For example:

public String someMethod(int x,char y){
    return new StringBuilder().append('y', x);    
}

But there isn't such method for StringBuilder or StringBuffer or etc. Can you give me any suggestions? Thanks in advance.

Updated: So, the solution will be:

public String someMethod(int x,char y){
    return new String(new char[x]).replace("\0", String.valueOf(y))  
}

Thanks for help!

Any reason why it has to be done without a loop? Any built-in function, if it were to exist, most likely uses a loop anyway. — Daniël Knippers
– Daniël Knippers, Commented Apr 18, 2014 at 7:50
If I would look at your code, I would start thinking like "what is s/he trying to achieve", soon followed by "Why no loop? There must be a reason for it". If you would just use a loop (while avoiding concatenation - use StringBuilder), it's obvious what you are trying to do, and it's the usual way. — stuXnet
– stuXnet, Commented Apr 18, 2014 at 8:05

merlin2011 · Accepted Answer · 2014-04-18 07:48:47Z

1

Try this. Here we are generating a new char[] which default initializes to all 0's, and then replacing these 0's with the character we want.

public class B {

    public static void main(String[] args) {            
        int x = 5;
        String y = "h";
        String result = new String(new char[x]).replace("\0", y);
        System.out.println(result);
    }
}

answered Apr 18, 2014 at 7:48

merlin2011

76.4k48 gold badges218 silver badges364 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

merlin2011 Over a year ago

@user3523579, I just updated it to use a variable instead of a literal, but it's the same thing.

fge Over a year ago

There is more simple than that: create a char[] and use Arrays.fill()

merlin2011 Over a year ago

@fge, Arrays.fill() returns void so that would require at least three lines (one to declare the char[], one to fill it, and one to make a string out of it), where my solution requires one line.

Totò · Accepted Answer · 2014-04-18 07:53:59Z

1

You can do

import java.util.Arrays;

public String someMethod(int x,char y){
    char[] a = new char[x];
    Arrays.fill(a, 0, x, y);
    return new String(a);
}

answered Apr 18, 2014 at 7:53

Totò

1,85415 silver badges21 bronze badges

Comments

stuXnet · Accepted Answer · 2014-04-18 08:09:09Z

1

As others are saying, it's not possible completely without a loop - you could hide it behind other methods, but they still use a loop.

If it's just for the sake of "more compact" code, you could write your own method to do exactly that - or you use third party libs like Apache Commons StringUtils : StringUtils.repeat(String str, int repeat) should do the job

Javadoc for StringUtils.repeat(...)

answered Apr 18, 2014 at 8:09

stuXnet

4,3493 gold badges25 silver badges31 bronze badges

Comments

Mikhail Kholodkov · Accepted Answer · 2018-09-27 01:15:25Z

1

Answering my own question almost 5 years later.

In Java 11 it can be done as following:

public String someMethod(int x, char y) {
    return String.valueOf(y).repeat(x);
}

answered Sep 27, 2018 at 1:15

Mikhail Kholodkov

25.4k17 gold badges64 silver badges81 bronze badges

Comments

Eric · Accepted Answer · 2014-04-18 07:45:17Z

0

Use StringBuffer & loop, without loop this can't be done.
Even you found a method that could do it without loop, inside it's still use loop.

answered Apr 18, 2014 at 7:45

Eric

25.8k26 gold badges168 silver badges232 bronze badges

Comments

Betlista · Accepted Answer · 2014-04-18 07:58:44Z

0

public String someMethod(int x,char y) {
    StringBuilder buff = new StringBuilder();
    return someMethod( x, y, buff );
}

public String someMethod(int x,char y, StringBuilder buff) {
    if (x == 0) return buff.toString();
    else {
        buff.append( y );
        return someMethod( x, y, buff );
    }
}

...but recursion is not better than loop if this is not a puzzle...

On the other hand, recursion is more general, when someone wants to remove loop comparing to some String realted functions (in this case new String(char[]) and replace())

edited Apr 18, 2014 at 7:58

answered Apr 18, 2014 at 7:51

Betlista

10.6k14 gold badges75 silver badges115 bronze badges

Comments

Ian Roberts · Accepted Answer · 2014-04-18 08:17:42Z

0

For java 8 you could use a stream:

Stream.generate(() -> String.valueOf(y))
      .limit(x)
      .collect(Collectors.joining()).toString()

answered Apr 18, 2014 at 8:17

Ian Roberts

123k17 gold badges177 silver badges191 bronze badges

Collectives™ on Stack Overflow

returning a String with X repeated characters without a loop

7 Answers 7

3 Comments

Comments

Comments

Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

7 Answers 7

3 Comments

Comments

Comments

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related