refactor: Use generics and return abstract superclasses where applicable

src/main/java/edu/ntnu/idatt2001/nicolahb/Army.java

@@ -14,11 +14,11 @@ import java.util.stream.Collectors;
  * Two armies fight each other.
  *
  * @author Nicolai Brand
- * @version 16.05.2022
+ * @version 20.05.2022
  */
 public class Army {
     private String name;
-    private ArrayList<Unit> units;
+    private final ArrayList<Unit> units;
 
     /**
      * Default constructor
@@ -40,10 +40,10 @@ public class Army {
      * @param units the units
      * @throws IllegalArgumentException the illegal argument exception
      */
-    public Army(String name, ArrayList<Unit> units) throws IllegalArgumentException {
+    public Army(String name, List<Unit> units) throws IllegalArgumentException {
         if (name.isBlank()) throw new IllegalArgumentException("Name can't be empty");
         this.name = name;
-        this.units = units;
+        this.units = (ArrayList<Unit>) units;
     }
 
     /**
@@ -178,7 +178,7 @@ public class Army {
      *
      * @return units, ArrayList<Unit>.
      */
-    public ArrayList<Unit> getUnits() {
+    public List<Unit> getUnits() {
         return units;
     }
 

src/main/java/edu/ntnu/idatt2001/nicolahb/gui/models/DataHolderSingleton.java

@@ -29,7 +29,7 @@ import java.io.IOException;
  * of the data.
  *
  * @author Nicolai H. Brand.
- * @version 19.05.2022
+ * @version 20.05.2022
  */
 public final class DataHolderSingleton {
 
@@ -43,7 +43,7 @@ public final class DataHolderSingleton {
     private static Army armyOneCopy;
     private static Army armyTwoCopy;
     private static Battle battle;
-    private static Logger battleLog = new Logger(true);
+    private static Logger<String> battleLog = new Logger(true);
 
     private final static StringProperty armyOnePath = new SimpleStringProperty("filename");
     private final static StringProperty armyTwoPath = new SimpleStringProperty("filename");

src/main/java/edu/ntnu/idatt2001/nicolahb/gui/models/Logger.java

@@ -14,8 +14,8 @@ import javafx.collections.ObservableList;
  * @author Nicolai H. Brand.
  * @version 20.05.2022.
  */
-public class Logger {
-    private final ObservableList<String> log;
+public class Logger<T> {
+    private final ObservableList<T> log;
     /* Will add new log items to index 0 of the array if reverse flag is set to true */
     private final boolean REVERSE_FLAG;
 
@@ -43,7 +43,7 @@ public class Logger {
      *
      * @param item String, the new item to be added to the log.
      */
-    public void addLogItem(String item) {
+    public void addLogItem(T item) {
         if (REVERSE_FLAG)
             log.add(0, item);
         else
@@ -59,7 +59,7 @@ public class Logger {
     }
 
     // getter
-    public ObservableList<String> getLog() {
+    public ObservableList<T> getLog() {
         return log;
     }
 }