use "invalid" instead of "unknown"

Author: AlvesJorge

exercises/concept/football-match-reports/.docs/instructions.md

@@ -27,11 +27,11 @@ FootballMatchReports.onField(10);
 // => "striker"
 ```
 
-## 2. Output "unknown" if the shirt number is not part of the official list
+## 2. Output "invalid" if the shirt number is not part of the official list
 
-Modify the `FootballMatchReports.onField()` method to return 'unknown' when a shirt number outside the range 1-11 is processed.
+Modify the `FootballMatchReports.onField()` method to return 'invalid' when a shirt number outside the range 1-11 is processed.
 
 ```java
 FootballMatchReports.onField(13);
-// => "unknown"
+// => "invalid"
 ```

exercises/concept/football-match-reports/.meta/src/reference/java/FootballMatchReports.java

@@ -30,7 +30,7 @@ public static String onField(int shirtNum) {
                 playerDescription = "striker";
                 break;
             default:
-                playerDescription = "unknown";
+                playerDescription = "invalid";
         }
         return playerDescription;
     }

exercises/concept/football-match-reports/src/test/java/FootballMatchReportsTest.java

@@ -67,15 +67,15 @@ public void test_right_wing() {
 
     @Test
     @Tag("task:2")
-    @DisplayName("The onField method returns 'unknown' for unknown shirt number")
+    @DisplayName("The onField method returns 'invalid' for invalid shirt number")
     public void test_exception() {
-        assertThat(FootballMatchReports.onField(13)).isEqualTo("unknown");
+        assertThat(FootballMatchReports.onField(13)).isEqualTo("invalid");
     }
 
     @Test
     @Tag("task:2")
-    @DisplayName("The onField method returns 'unknown' for negative shirt number")
+    @DisplayName("The onField method returns 'invalid' for negative shirt number")
     public void test_exception_negative_number() {
-        assertThat(FootballMatchReports.onField(-1)).isEqualTo("unknown");
+        assertThat(FootballMatchReports.onField(-1)).isEqualTo("invalid");
     }
 }