java how to make a string lowercase

1/* to find the lowercase or uppercase of a string, 
2* we just .toLowerCase() or .toUpperCase()
3*/
4
5public class CaseDemonstration {
6  public static void main(String[] args) {
7    
8   	String testString = "THIS IS AN EXAMPLE OF A STRING";
9    String testStringLower = testString.toLowerCase(); // make a string lowercase
10    System.out.println(testStringLower); // "this is an example of a string"
11    String testStringUpper = testStringLower.toUpperCase(); // make it upper again
12    System.out.println(testStringUpper); // "THIS IS AN EXAMPLE OF A STRING"
13    
14  }
15}