Given a sentence with multiple spaces between words. Remove the extra spaces so that the sentence will have exactly one space between words

Question

The question is clear. Code should be in Java and without using Regex (In case someone didn't notice, that's not a duplicate, I'm asking for a way to do it without regex).

input: This is  a string     with more than   one space between words.

output: This is a string with more than one space between words.

Is there a better way than doing it this way ?

public static String delSpaces(String str){
    StringBuilder sb = new StringBuilder(str);
    ArrayList<Integer> spaceIndexes = new ArrayList<>();

    for ( int i=0; i < sb.length(); i++ ){
        if ( sb.charAt(i) == ' ' && sb.charAt(i-1) == ' '){
            spaceIndexes.add(i);
        }
    }

    for (int i = 0; i < spaceIndexes.size(); i++){
        sb.deleteCharAt(spaceIndexes.get(i)-i);
    }
    return new String(sb.toString());
}

Rustam · Accepted Answer · 2014-10-25T19:05:50.643

11

use str.replaceAll("\\s+"," "); // simplest way using regular expression

2nd way :

public static String delSpaces(String str){    //custom method to remove multiple space
        StringBuilder sb=new StringBuilder();
        for(String s: str.split(" ")){

            if(!s.equals(""))        // ignore space
             sb.append(s+" ");       // add word with 1 space

        }
        return new String(sb.toString());
    }

3rd way :

public static String delSpaces(String str){
        int space=0;
        StringBuilder sb=new StringBuilder();
        for(int i=0;i<str.length();i++){
            if(str.charAt(i)!=' '){
                sb.append(str.charAt(i));  // add character
                space=0;
            }else{
                space++;
                if(space==1){       // add 1st space
                    sb.append(" ");
                }
            }
        }
        return new String(sb.toString());
    }

edited Oct 25 '14 at 19:05

answered Oct 25 '14 at 18:26

Rustam

6,485
1
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25

Rustam, StringBuilder doesn't have a replaceAll method, that's for Strings. And replaceAll uses Regex, I don't want that. Thanks anyway. – oudouz Oct 25 '14 at 18:37
As i see your `str` is `String` not `StringBuilder`. – Rustam Oct 25 '14 at 18:40
Yeah, but it was the method argument, you don't expect someone to pass a StringBuilder as an argument, I used the String to instantiate an SB object inside the method. – oudouz Oct 25 '14 at 18:43
@oudouz hope 2nd answer is what you looking for. – Rustam Oct 25 '14 at 18:56

score 4 · Answer 2 · answered Oct 25 '14 at 18:28

4

str = str.replaceAll("\\s+", " "); would do the trick with regex. This is much faster than you having to write a method to dos.

answered Oct 25 '14 at 18:28

kuriouscoder

5,394
7
26
40

I know it's faster, but I want an Algo for that. I want to write my own method. – oudouz Oct 25 '14 at 18:37

Prakhar · Answer 3 · 2014-10-25T18:52:37.530

1

class Try 
{
    public static void main(String args[])
    {
        String str = "This is  a string     with more than   one space between words.";
        char[] c = str.toCharArray();
        String str1 = "";
        for(int i = 0;i<str.length()-1;i++)
        {
            if((c[i] == ' '&& c[i+1] != ' ') || (c[i] != ' '))
                str1 += c[i];
        }

        System.out.println(str1);
    }
}

This works easily.

edited Oct 25 '14 at 18:52

answered Oct 25 '14 at 18:33

Prakhar

530
10
24

String.replaceAll() uses regex for the first argument Prakhar. – oudouz Oct 25 '14 at 18:38
oudouz, may be this could help – Prakhar Oct 25 '14 at 18:52
1

@Prakhar avoid adding character to `String` variable inside loop because each time new `String` will be created. better use `StringBuilder` or `StringBuffer` – Rustam Oct 25 '14 at 19:11

Given a sentence with multiple spaces between words. Remove the extra spaces so that the sentence will have exactly one space between words

3 Answers3