kevin@inspiron-15-5510:~/Desktop/check_style$ cat config.xml 
<?xml version="1.0"?>
<!DOCTYPE module PUBLIC "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
        "https://checkstyle.org/dtds/configuration_1_3.dtd">

<module name="Checker">
    <module name="TreeWalker">
        <module name="FallThrough">
            <property name="checkLastCaseGroup" value="true"/>
        </module>
    </module>
</module>

kevin@inspiron-15-5510:~/Desktop/check_style$ cat Test.java
     1  public class Test {
     2      void method(int i) {
     3        switch(i) {
     4          case 0: 
     5            int j = 22; // fallthru  
     6          case 1: /* line no :- 6 */
     7            int k = 2;
     8            break;
     9          case 2:
    10            i++;
    11            // fall thru  
    12          case 3: 
    13            i++;
    14            break;  
    15        }   
    16      }
    17      
    18      void foo(int i){
    19        switch(i) {
    20          case 1:
    21            int fallthru = 2; // fallthru
    22          case 2:   
    23            int fallthrough = 2; //            fall thru
    24          case 3: 
    25            break;
    26          case 4:
    27            int fallthru2 = 3;
    28            //     fall   -   thru
    29          case 5: 
    30            int fallthru3 = 4; // This is a fallthru comment
    31          case 6: 
    32            int fallthru4 = 5; // falldown
    33            default:
    34          }
    35      }
    36    }

kevin@inspiron-15-5510:~/Desktop/check_style$ java \
   -jar /home/kevin/Downloads/checkstyle-10.12.2-all.jar -c config.xml Test.java
Starting audit...
[ERROR] Test.java:22:7: Fall through from previous branch of the switch statement. [FallThrough]
[ERROR] Test.java:24:7: Fall through from previous branch of the switch statement. [FallThrough]
[ERROR] Test.java:29:7: Fall through from previous branch of the switch statement. [FallThrough]
[ERROR] Test.java:31:7: Fall through from previous branch of the switch statement. [FallThrough]
[ERROR] Test.java:33:9: Fall through from previous branch of the switch statement. [FallThrough]
Audit done.
Checkstyle ends with 5 errors.