Remove spaces from a string in Java

Understanding String Manipulation

Removing spaces from a string means eliminating all whitespace characters.

We will explore three different methods to achieve this in Java.

Method 1: Using a Loop

This method iterates through the string and copies only non-space characters.

public class RemoveSpaces {
    public static String removeSpaces(String str) {
        StringBuilder result = new StringBuilder();
        for (char c : str.toCharArray()) {
            if (c != ' ') {
                result.append(c);
            }
        }
        return result.toString();
    }

    public static void main(String[] args) {
        String str = "Hello World!";
        System.out.println("Filtered String: " + removeSpaces(str));
    }
}
            

Method 2: Using Recursion

This method removes spaces recursively.

public class RemoveSpacesRecursive {
    public static String removeSpacesRecursive(String str, int index) {
        if (index == str.length()) {
            return "";
        }
        char c = str.charAt(index);
        return (c == ' ' ? "" : c) + removeSpacesRecursive(str, index + 1);
    }

    public static void main(String[] args) {
        String str = "Java Programming";
        System.out.println("Filtered String: " + removeSpacesRecursive(str, 0));
    }
}
            

Method 3: Using ReplaceAll()

This method uses Java's built-in replaceAll() function.

public class RemoveSpacesReplaceAll {
    public static void main(String[] args) {
        String str = "Remove spaces";
        String result = str.replaceAll(" ", "");
        System.out.println("Filtered String: " + result);
    }
}