Java Programs›Strings›Remove Spaces from a String

Remove Spaces from a String in Java

beginner· Strings · String Manipulation

Problem

Removing spaces means dropping every space character from a string while keeping every other character in place.

Given a string, remove every space character from it.

Input

Java Programming Language

Output

JavaProgrammingLanguage

Java Program

Java

public class RemoveSpaces {
    public static void main(String[] args) {
        String str = "Java Programming Language";
        StringBuilder result = new StringBuilder();
        for (char c : str.toCharArray()) {
            if (c != ' ') result.append(c); // skip the space character entirely
        }
        System.out.println(result.toString());
    }
}

▶ Run Code

Output

JavaProgrammingLanguage

Core Logic

A single pass through the string, appending every character except a space, builds the space-free result.

How It Works

1A for-each loop visits each character of the string in turn.
2if (c != ' ') checks whether the current character is anything other than a space.
3Characters that pass the check are appended to a StringBuilder; spaces are simply skipped.
4The final StringBuilder holds every original character except the spaces.

For "Java Programming Language", the two spaces between words are skipped, producing "JavaProgrammingLanguage".

💡

Key Point: This checks only the literal space character — tabs or newlines would still be appended to the result, unlike a check based on Character.isWhitespace().

Complexity

Time Complexity: O(n)Space Complexity: O(n)

Why: Each character is visited once and the result buffer grows to hold every non-space character, which can be up to n.

Key Concepts

char comparisonStringBuilderfor-each loop

Approach 2: Using replace()

Java

public class RemoveSpacesBuiltin {
    public static void main(String[] args) {
        String str = "Java Programming Language";
        // replace() swaps every space for an empty string, which deletes it
        System.out.println(str.replace(" ", ""));
    }
}

▶ Run Code

Output

JavaProgrammingLanguage

Core Logic

In real code, there's no reason to loop manually — replace() already removes every matching character in one call.

How It Works

1str.replace(" ", "") takes the space character as the target and an empty string as the replacement.
2Every occurrence of a space is replaced with nothing, which is the same as deleting it.
3The result is a brand-new string with no spaces left.

"Java Programming Language".replace(" ", "") returns "JavaProgrammingLanguage" in a single call.

💡

Key Point: This is the version to actually use — the manual loop exists only to show what replace() is conceptually doing under the hood.

Complexity

Time Complexity: O(n)Space Complexity: O(n)

Why: replace() still has to scan the whole string and build a new one without the matched character, but that work happens inside the JDK instead of your own loop.

Key Concepts

String.replace()

Approach 3: Java 8

Java

import java.util.stream.Collectors;

public class RemoveSpacesStream {
    public static void main(String[] args) {
        String str = "Java Programming Language";
        // Keeps every character except spaces, then joins them back into a String
        String result = str.chars()
            .filter(c -> c != ' ')
            .mapToObj(c -> String.valueOf((char) c))
            .collect(Collectors.joining());
        System.out.println(result);
    }
}

▶ Run Code

Output

JavaProgrammingLanguage

Core Logic

The same skip-the-spaces logic can filter a stream of character codes down to the non-space ones, then join what's left.

How It Works

1str.chars() returns an IntStream of the string's character codes.
2.filter(c -> c != ' ') keeps every code except the space character.
3.mapToObj(c -> String.valueOf((char) c)) converts each surviving code back into a one-character String.
4.collect(Collectors.joining()) concatenates them all back into a single result string.

Filtering "Java Programming Language" drops both spaces, and joining what's left reassembles "JavaProgrammingLanguage".

💡

Key Point: The filter condition is the exact same check the loop version uses — streams just change how it's applied across the string.

Complexity

Time Complexity: O(n)Space Complexity: O(n)

Why: The stream still visits every character once, and Collectors.joining() builds a result string holding every non-space character.

Key Concepts

Streamchars()filter()Collectors.joining()

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