The file you should be modifying, Lab.java, can be found in your editor's file explorer, under the folders src/main/java. All lab instructions are contained within. While you may freely modify Application.java, no changes made to Application.java will solve the lab.

You should run the test cases, which will verify that your code was written correctly, by clicking the 'run' button in the HelloWorldTest.java file in src/test/java. The test output will determine if your solution was correct or incorrect by comparing 'expected' and 'actual' results.

You should NEVER change the code in test files, as you would be likely to break the lab structure.