Exercise using exception handling in Explore (Game) program

• Download the Explore jar file from examples section and open in BlueJ (Click Project, Open ZIP/JAR).
• Define a checkWater method in the Explorer class as specified below, and call it from the move method, right after the destination location (dest) is computed, to see if the Explorer is going to fall in the water, i.e. off the island. Your checkWater method of Explorer may invoke the method onTheIsland of Island, to see if the desired location is on the island or not.

      /**
       * checkWater: check if the specified location is in the water (i.e. not on the specified island) and if so, throw a GameOverException; otherwise do nothing.
       * @param an Island
       * @param a Location 
       * @return none
       */
      public void checkWater(Island isle, Location loc)
      {
      }
  
      

• You may refer to the code in Explorer's move method that throws GameOverException when the user chooses to quit, to see how to throw an exception. Currently, GameOverException is defined in a separate class as a Runtime exception. Once you get this to work, you may (optionally) see what happens when you change it to a Checked exception, i.e. GameOverException extends Exception (rather than having it extend RuntimeException).
• Test using JUnit (e.g. using ExplorerTest.java):

      // Test that GameOverException is thrown appropriately
      @Test
      public void testGameOverByFallingInWater() {
  
  			try {
  			        Island isle = new Island();
  			        Location dest = new Location(0, -1); // a location that is not on the island
  				_explorer.checkWater(isle, dest);
  
  				// If we reach this point in the code, that means the exception was not thrown as expected, so this test case fails.
  				fail(); 
  			}
  			catch (GameOverException e) {
  				System.out.println("GameOverException on testGameOverByFallingInWater");;
  				e.printStackTrace();
  			}
  			
      }
  

  • An alternative way to test that a GameOverException was thrown appropriately:

        @Test
        public void whenExceptionThrown_thenAssertionSucceeds() {
            Exception exception = assertThrows(GameOverException.class, () -> {   
                Island isle = new Island();
                Location dest = new Location(0, -1); // a location that is not on the island
                _explorer.checkWater(isle, dest);
            });
            
            String expectedMessage = "You fell in the water.";
            String actualMessage = exception.getMessage();
        
            assertTrue(actualMessage.contains(expectedMessage));
        }