How to remove all white spaces in java

To remove all white spaces from a string in Java, you can use the replaceAll method of the String class, along with a regular expression that matches any white space character (including spaces, tabs, and line breaks):

String str = "   This   is   a   test   ";
str = str.replaceAll("\\s", "");  // str is now "Thisisatest"

You can also use the trim method to remove leading and trailing white spaces from the string:

String str = "   This   is   a   test   ";
str = str.trim();  // str is now "This   is   a   test"

Keep in mind that the trim method only removes leading and trailing white spaces, and not white spaces within the string. To remove all white spaces within the string as well, you can use the replaceAll method with a regular expression as shown above.