In Java, the trim() method is a built-in method of the String class that is used to remove any leading and trailing white space from a string. The trim() method returns a new string with the leading and trailing white space removed.

Here's an example:

String str = "   hello world   ";
String trimmedStr = str.trim();
System.out.println(trimmedStr); // prints "hello world"

In the example above, we create a string str that contains leading and trailing white space. We then call the trim() method on the string to remove the white space and assign the result to a new string variable trimmedStr. Finally, we print the trimmedStr variable, which outputs "hello world" without any leading or trailing white space.

Note that the trim() method does not modify the original string, but rather returns a new string with the leading and trailing white space removed. If the string does not contain any leading or trailing white space, the trim() method returns the original string.