Remove whitespace from an array of string

June 3, 2023

Remove whitespace from an array of string.

While creating an array of string from a sentence, I’m encountering multiple spaces and need to remove them in order to create a new reverse sentence from the given sentence. How do I remove extra spaces in the middle of two words?
Example: a good example
How do I remove two spaces in between good and example ?

Here is the code I’m using:

public class reverseString {
    public static void main(String[] args) {
        String s = "a good   example";
        String ans = revString(s);
        System.out.println(ans);
    }
    static String revString(String s) {
        String[] arr = s.split(" ");
        List<String> list = new ArrayList<String>();
        StringBuilder ans = new StringBuilder();
        for (int i = arr.length - 1; i >= 0; i--) {
            if (arr[i] == null) {
                continue;
            } else {
                ans.append(arr[i].trim());
                // ans.append(" ");
            }
        }
        String is = ans.toString();
        return is.trim();
    }
}

The expected output was: example good a
The output I’m getting is: example good a
Comparing the string at the I-th index with " " should result in continuation of the loop. Instead it jumps to the else condition.

>Solution :

The parameter to method split (of class java.lang.String) is a regular expression. Just add a + (i.e. "plus" symbol – which means one or more) to the value of the parameter.

import java.util.ArrayList;
import java.util.List;

public class ReverseString {

    public static void main(String[] args) {
        String s = "a good   example";
        String ans = revString(s);
        System.out.println(ans);

    }

    static String revString(String s) {
        String[] arr = s.split(" +"); // CHANGE HERE - added '+'
        List<String> list = new ArrayList<String>();
        StringBuilder ans = new StringBuilder();
        for (int i = arr.length - 1; i >= 0; i--) {
            if (arr[i] == null) {
                continue;
            }
            else {
                ans.append(arr[i].trim());
                ans.append(" ");
            }
        }
        String is = ans.toString();
        return is.trim();
    }
}

Running the above code produces the following output: