trim() vs strip() in java

How to remove whitespace, specifically leading and trailing whitespace. For example, here you have strings with whitespace at the start and the end. To remove them, we can simply invoke the trim method on each, like so. Run this code.

package strings;

public class RemoveSpaceDemo {

public static void main(String... args){

  System.out.println("hello     ".trim + "    there".trim());
  
  //hellothere

  }
}

And indeed, we see that these words are concatenated together without any whitespace between them. But, I could also use the strip method, added in Java 11, and the result will be the same.

package strings;

public class RemoveSpaceDemo {

public static void main(String... args){

  System.out.println("hello     ".strip()+ "    there".trim());
  
  //hellothere

  }
}

So what’s the difference between these two? Here’s a super‑quick simplified reminder of computer science basics. Computers started with ASCII 128 characters, just enough to fit on an old keyboard. These included numbers and letters, as well as tab, line feed, carriage return, and, of course, the space invisible characters. Then all the other languages and alphabets and signs needed to be included, so Unicode had to be created, which is essentially a huge superset of ASCII. The first 128 characters in Unicode are the same as in ASCII, so the Space character or graphic is at position 32, and its code in Unicode is 0020. This is important because if we look at the Java dock of trim, available since Java 1, it reads that it considers whitespace as any character whose code point is less than or equal to Unicode 0020, the Space character. So trim removes spaces, tabs, line feeds, and carriage returns. And that’s great. But Unicode kept evolving. And as years went by, all sorts of new whitespace characters got added. If you search for Unicode space characters, you’ll see that there’s a lot of them. The only difference between many of them is their width. And it’s fine to add more characters. But as you might know, Java avoids breaking changes, so changing the implementation of trim and making it remove extra space characters would have been dangerous and could break a lot of existing software. That is why they added strip. To sum up, strip is a Unicode‑aware evolution of trim and its sets some low‑level control characters, it will remove many more whitespace characters that got added to Unicode over time. My advice is to prefer strip over trim where you can. To see it in action, here we have a single escaped character, the so‑called N space. We will use the isWhitespace method to check if it’s considered whitespace, and it will be. And we’ll try to trim it and strip it. Trim will not remove it, but strip will.

package strings;

public class RemoveSpaceDemo {

public static void main(String... args){

  System.out.println("hello     ".strip()+ "    there".trim());

  char space = '\u2002';

  System.out.println("\\u2002 is whitespace: " + Character.isWhitespace(space));

  
  System.out.println("hello\u2002".trim() + "\u2002there".trim());
  System.out.println("hello\u2002".strip() + "\u2002there".strip());

   /*output ->
    hellothere
    \u2002 is whitespace: true
    hello there
    hellothere

    */

  }
}

Run the code. And see here, the n space is indeed considered to be a Whitespace, trim failed to remove, it but strip did.