Use enums more/better

src/edu/kit/informatik/CoachType.java

@@ -5,6 +5,19 @@ public enum CoachType {
     FREIGHT,
     SPECIAL;
 
+    public static CoachType parse(String value) {
+        switch (value) {
+            case "passenger":
+                return PASSENGER;
+            case "freight":
+                return FREIGHT;
+            case "special":
+                return SPECIAL;
+            default:
+                return null;
+        }
+    }
+
     @Override
     public String toString() {
         switch (this) {

src/edu/kit/informatik/EngineType.java

@@ -0,0 +1,32 @@
+package edu.kit.informatik;
+
+/**
+ * Type of locomotive. Can be either diesel, steam or electrical.
+ */
+public enum EngineType {
+    /**
+     * Diesel engine.
+     */
+    DIESEL,
+    /**
+     * Steam engine.
+     */
+    STEAM,
+    /**
+     * Electrical engine.
+     */
+    ELECTRICAL;
+
+    public static EngineType parse(String value) {
+        switch (value) {
+            case "diesel":
+                return DIESEL;
+            case "steam":
+                return STEAM;
+            case "electrical":
+                return ELECTRICAL;
+            default:
+                return null;
+        }
+    }
+}

src/edu/kit/informatik/command/CommandFactory.java

@@ -1,6 +1,7 @@
 package edu.kit.informatik.command;
 
 import edu.kit.informatik.CoachType;
+import edu.kit.informatik.EngineType;
 import edu.kit.informatik.Point;
 import edu.kit.informatik.Terminal;
 
@@ -120,7 +121,7 @@ public class CommandFactory {
                 Terminal.printError("invalid create engine argument syntax");
                 return null;
             }
-            String type = matcher.group(1);
+            EngineType type = EngineType.parse(matcher.group(1));
             String series = matcher.group(2);
             if (series.startsWith("W")) {
                 Terminal.printError("invalid engine class/series");
@@ -144,20 +145,11 @@ public class CommandFactory {
                 Terminal.printError("invalid create coach arguments");
                 return null;
             }
+            CoachType type = CoachType.parse(matcher.group(1));
             int length = Integer.parseInt(matcher.group(2));
             boolean couplingFront = Boolean.parseBoolean(matcher.group(3));
             boolean couplingBack = Boolean.parseBoolean(matcher.group(4));
-            switch (matcher.group(1)) {
-                case "passenger":
-                    return new CreateCoach(CoachType.PASSENGER, length, couplingFront, couplingBack);
-                case "freight":
-                    return new CreateCoach(CoachType.FREIGHT, length, couplingFront, couplingBack);
-                case "special":
-                    return new CreateCoach(CoachType.SPECIAL, length, couplingFront, couplingBack);
-                default:
-                    throw new IllegalStateException("regex matched unmatchable argument");
-
-            }
+            return new CreateCoach(type, length, couplingFront, couplingBack);
         } else if (command.startsWith(LIST_COACHES)) {
             if (command.length() > LIST_COACHES.length()) {
                 Terminal.printError("too many list coaches arguments");

src/edu/kit/informatik/command/CreateEngine.java

@@ -9,7 +9,7 @@ import edu.kit.informatik.*;
  * @version 1.0
  */
 public class CreateEngine extends Command {
-    private final String type;
+    private final EngineType type;
     private final String series;
     private final String name;
     private final int length;
@@ -25,7 +25,7 @@ public class CreateEngine extends Command {
      * @param couplingFront whether the new engine should have a front coupling
      * @param couplingBack whether the new engine should have a back coupling
      */
-    public CreateEngine(final String type, final String series, final String name, final int length, final boolean couplingFront, final boolean couplingBack) {
+    public CreateEngine(final EngineType type, final String series, final String name, final int length, final boolean couplingFront, final boolean couplingBack) {
         this.type = type;
         this.series = series;
         this.name = name;
@@ -38,18 +38,17 @@ public class CreateEngine extends Command {
     public void apply(final ModelRailwaySimulation simulation) {
         final Engine engine;
         switch (type) {
-            case "electrical":
+            case ELECTRICAL:
                 engine = new ElectricalEngine(series, name, length, couplingFront, couplingBack);
                 break;
-            case "steam":
+            case STEAM:
                 engine = new SteamEngine(series, name, length, couplingFront, couplingBack);
                 break;
-            case "diesel":
+            case DIESEL:
                 engine = new DieselEngine(series, name, length, couplingFront, couplingBack);
                 break;
             default:
-                Terminal.printError("invalid engine type");
-                return;
+                throw new IllegalStateException("engine type is null!");
         }
         if (simulation.createEngine(engine)) {
             Terminal.printLine(engine.getIdentifier());