java how to make a string lowercase

/* to find the lowercase or uppercase of a string, 
* we just .toLowerCase() or .toUpperCase()
*/

public class CaseDemonstration {
  public static void main(String[] args) {
    
   	String testString = "THIS IS AN EXAMPLE OF A STRING";
    String testStringLower = testString.toLowerCase(); // make a string lowercase
    System.out.println(testStringLower); // "this is an example of a string"
    String testStringUpper = testStringLower.toUpperCase(); // make it upper again
    System.out.println(testStringUpper); // "THIS IS AN EXAMPLE OF A STRING"
    
  }
}