Java String trim()

class Main {
  public static void main(String[] args) {
    String str1 = "   Learn Java Programming      ";

    System.out.println(str1.trim());

  }
}

// Output: Learn Java Programming

Syntax of trim()

The syntax of the string trim() method is:

string.trim()

Here, string is an object of the String class.

trim() Parameters

• the trim() method doesn't take any parameters

trim() Return Value

• returns a string with leading and trailing whitespace removed
• returns the original string if there is no whitespace in the start or the end of the string

Note: In programming, whitespace is any character or series of characters that represent horizontal or vertical space. For example: space, newline \n, tab \t, vertical tab \v etc.

Example: Java String trim()

class Main {
  public static void main(String[] args) {
    String str1 = "     Learn   Java Programming ";
    String str2 = "Learn\nJava Programming\n\n   ";

    System.out.println(str1.trim());
    System.out.println(str2.trim());

  }
}

Output

Learn  Java Programming
Learn
Java Programming

Here, str1.trim() returns

"Learn   Java Programming"

Similarly, str2.trim() returns

"Learn\nJava Programming"

As you can see from the above example, the trim() method only removes the leading and trailing whitespace. It doesn't remove whitespace that appears in the middle.

Remove All Whitespace Characters

If you need to remove all whitespace characters from a string, you can use the String replaceAll() method with proper regex.

class Main {
  public static void main(String[] args) {
    String str1 = "Learn\nJava \n\n   ";
    String result;

    // replace all whitespace characters with empty string
    result = str1.replaceAll("\\s", "");

    System.out.println(result);   // LearnJava
  }
}