How to remove white spaces from a String

Very often, you will come across programming scenarios where you will need to remove all white spaces from a String.  In this article, we will see how to remove whitespaces from a String in Java.

Using String.trim

The String class has a method trim. You can use this to remove leading and trailing white spaces from a String. The following code demonstrates this:

String str1 = "   Hello World  ";
System.out.println(str1);
System.out.println(str1.trim());

This code creates a String str1 that has leading and trailing whitespaces. It then invokes the trim method. So this code prints the following output:

     Hello World 
Hello World

Using String.replace

Note that the trim method removes only the leading and trailing white spaces. It does not remove white spaces that are in between the String. There is a replace method on the String class that replaces the specified character with some other character. You can use this method to remove the spaces in a String. The following code demonstrates this:

String str1 = "   Hello World  ";
String str2 = str1.replace(" ", "");
System.out.println(str2);

This code invokes the str.replace method. The first argument is the character that needs to be replaced, here a space (” “) is specified. The second argument is the new character, here an empty String (“”) is specified. So this code prints the following output:

HelloWorld

Using String.replaceAll

In addition to the replace method, there is also a replaceAll method on the String class. It accepts as parameters  a regular expression and a replacement value. It replaces each substring that matches the regular expression with the replacement value. The following code demonstrates this:

String str1 = "   Hello World  ";
String str2 = str1.replaceAll("\\s", "");
System.out.println(str2);

This code invokes the str.replaceAll method. The first argument is a regular expression that matches white spaces.,The second argument is an empty String (“”) , which is the replacement value. So this code prints the following output:

HelloWorld

Conclusion

So in this article, we saw how you can remove all the whitespaces in a String in Java. We saw how the trim(), replace() and replaceAll() methods can be used to remove whitespaces.