Improve CardAdapter Handling and Validations

examples/src/main/java/com/squareup/moshi/recipes/MultipleFormats.java

@@ -28,14 +28,14 @@
 import java.io.IOException;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
+import java.util.Map;
 
 public final class MultipleFormats {
   public void run() throws Exception {
-    Moshi moshi =
-        new Moshi.Builder()
-            .add(new MultipleFormatsCardAdapter())
-            .add(new CardStringAdapter())
-            .build();
+    Moshi moshi = new Moshi.Builder()
+        .add(new MultipleFormatsCardAdapter())
+        .add(new CardStringAdapter())
+        .build();
 
     JsonAdapter<Card> cardAdapter = moshi.adapter(Card.class);
 
@@ -47,59 +47,69 @@ public void run() throws Exception {
     System.out.println(cardAdapter.toJson(new Card('5', Suit.CLUBS)));
   }
 
-  /** Handles cards either as strings "5D" or as objects {"suit": "SPADES", "rank": 5}. */
+  /**
+   * Handles cards either as strings "5D" or as objects {"suit": "SPADES", "rank":
+   * 5}.
+   */
   public final class MultipleFormatsCardAdapter {
     @ToJson
     void toJson(JsonWriter writer, Card value, @CardString JsonAdapter<Card> stringAdapter)
         throws IOException {
+      if (value == null || value.suit == null || value.rank == 0) {
+        throw new JsonDataException("Invalid card: " + value);
+      }
       stringAdapter.toJson(writer, value);
     }
 
     @FromJson
     Card fromJson(
         JsonReader reader,
         @CardString JsonAdapter<Card> stringAdapter,
-        JsonAdapter<Card> defaultAdapter)
-        throws IOException {
+        JsonAdapter<Card> defaultAdapter) throws IOException {
       if (reader.peek() == JsonReader.Token.STRING) {
         return stringAdapter.fromJson(reader);
-      } else {
-        return defaultAdapter.fromJson(reader);
       }
+      return defaultAdapter.fromJson(reader);
     }
   }
 
   /** Handles cards as strings only. */
   public final class CardStringAdapter {
+    private static final Map<Character, Suit> SUIT_MAP = Map.of(
+        'C', Suit.CLUBS,
+        'D', Suit.DIAMONDS,
+        'H', Suit.HEARTS,
+        'S', Suit.SPADES);
+
     @ToJson
     String toJson(@CardString Card card) {
+      if (card == null || card.suit == null || card.rank == 0) {
+        throw new JsonDataException("Invalid card: " + card);
+      }
       return card.rank + card.suit.name().substring(0, 1);
     }
 
     @FromJson
     @CardString
     Card fromJson(String card) {
-      if (card.length() != 2) throw new JsonDataException("Unknown card: " + card);
+      if (card == null || card.length() != 2) {
+        throw new JsonDataException("Invalid card format: " + card);
+      }
 
       char rank = card.charAt(0);
-      switch (card.charAt(1)) {
-        case 'C':
-          return new Card(rank, Suit.CLUBS);
-        case 'D':
-          return new Card(rank, Suit.DIAMONDS);
-        case 'H':
-          return new Card(rank, Suit.HEARTS);
-        case 'S':
-          return new Card(rank, Suit.SPADES);
-        default:
-          throw new JsonDataException("unknown suit: " + card);
+      Suit suit = SUIT_MAP.get(card.charAt(1));
+      if (suit == null) {
+        throw new JsonDataException("Unknown suit: " + card.charAt(1));
       }
+
+      return new Card(rank, suit);
     }
   }
 
   @Retention(RetentionPolicy.RUNTIME)
   @JsonQualifier
-  @interface CardString {}
+  @interface CardString {
+  }
 
   public static void main(String[] args) throws Exception {
     new MultipleFormats().run();