Java String trim() method

The trim() method in Java is used to remove leading and trailing whitespace (spaces, tabs, and other whitespace characters) from a string. However, it does not remove whitespace between words or characters inside the string.

trim( ) is used to remove any leading or trailing whitespace that may have inadvertently been entered by the user.

Syntax:


public String toLowerCase()

Note:

It returns a new string with the leading and trailing whitespace removed. If there is no leading or trailing whitespace, the original string is returned unchanged.

Example:


public class Main {
    public static void main(String[] args) {
        // Example string with leading and trailing spaces
        String str = "   How r you?   ";
        
        // Trim leading and trailing whitespace
        String trimmedStr = str.trim();
        
        System.out.println("Original String: '" + str + "'");  // Output: '   How r you?   '
        System.out.println("Trimmed String: '" + trimmedStr + "'");  // Output: 'How r you?'
    }
}

Output:

Original String: ‘ How r you? ‘
Trimmed String: ‘How r you?’

If string contain only spaces

If the string contains only spaces (or whitespace characters), the trim() method will return an empty string.


public class Main {
    public static void main(String[] args) {
        // Example string with leading and trailing spaces
        String str = "   ";
        String trimmedStr = str.trim();
        System.out.println(trimmedStr);  // Output: ''
    }
}

Java String trim() method – Interview Questions

Q 1: What is the purpose of trim() method?

Ans: It removes leading and trailing whitespaces from a string.

Q 2: Does trim() remove spaces in the middle?

Ans: No, it only removes spaces at the beginning and end.

Q 3: What type of value does trim() return?

Ans: A new trimmed string.

Q 4: Does trim() change the original string?

Ans: No, strings are immutable.

Q 5: When is trim() commonly used?

Ans: For input validation and data cleaning.