Made JsonParser implement Iterator

gson/src/main/java/com/google/gson/JsonParserAsync.java

@@ -18,18 +18,21 @@ package com.google.gson;
 import java.io.EOFException;
 import java.io.Reader;
 import java.io.StringReader;
+import java.util.Iterator;
 
 /**
  * A parser that allows reading of multiple {@link JsonElement}s from the specified reader
- * asynchronously.
+ * asynchronously. This class is not thread-safe.
  *
  * @author Inderjeet Singh
  * @author Joel Leitch
  * @since 1.4
  */
-public final class JsonParserAsync {
+public final class JsonParserAsync implements Iterator<JsonElement> {
 
   private final JsonParserJavacc parser;
+  private boolean eof;
+  private JsonElement nextElement;
 
   /**
    * @param json The string containing JSON elements concatenated to each other.
@@ -45,6 +48,8 @@ public final class JsonParserAsync {
    */
   public JsonParserAsync(Reader reader) {
     parser = new JsonParserJavacc(reader);      
+    eof = false;
+    nextElement = null;
   }
   
   /**
@@ -54,7 +59,15 @@ public final class JsonParserAsync {
    * @throws JsonParseException if the incoming stream is malformed JSON.
    * @since 1.4
    */
-  public JsonElement nextElement() throws JsonParseException {
+  public JsonElement next() throws JsonParseException {
+    if (eof) {
+      return null;
+    }
+    if (nextElement != null) {
+      JsonElement returnValue = nextElement;
+      nextElement = null;
+      return returnValue;
+    }
     try {
       JsonElement element = parser.parse();
       return element;
@@ -68,10 +81,20 @@ public final class JsonParserAsync {
       throw new JsonParseException("Failed parsing JSON source to Json", e);
     } catch (JsonParseException e) {
       if (e.getCause() instanceof EOFException) {
+        eof = true;
         return null;
       } else {
         throw e;
       }
     }
-  }    
+  }
+
+  public boolean hasNext() {
+    nextElement = next();
+    return nextElement != null;
+  }
+
+  public void remove() {
+    throw new UnsupportedOperationException();
+  }
 }

gson/src/test/java/com/google/gson/JsonParserAsyncTest.java

@@ -1,5 +1,8 @@
 package com.google.gson;
 
+import java.util.Enumeration;
+import java.util.Iterator;
+
 import junit.framework.TestCase;
 
 /**
@@ -11,9 +14,18 @@ public class JsonParserAsyncTest extends TestCase {
   
   public void testParseTwoStrings() {
     JsonParserAsync parser = new JsonParserAsync("'one' 'two'");
-    String actualOne = parser.nextElement().getAsString();
+    String actualOne = parser.next().getAsString();
     assertEquals("one", actualOne);
-    String actualTwo = parser.nextElement().getAsString();
+    String actualTwo = parser.next().getAsString();
     assertEquals("two", actualTwo);
   }
+  
+  public void testIterator() {
+    Iterator<JsonElement> parser = new JsonParserAsync("'one' 'two'");
+    assertTrue(parser.hasNext());
+    assertEquals("one", parser.next().getAsString());
+    assertTrue(parser.hasNext());
+    assertEquals("two", parser.next().getAsString());
+    assertFalse(parser.hasNext());
+  }
 }

gson/src/test/java/com/google/gson/functional/ReadersWritersTest.java

@@ -93,9 +93,9 @@ public class ReadersWritersTest extends TestCase {
     writer.write(gson.toJson("two").toCharArray());
     CharArrayReader reader = new CharArrayReader(writer.toCharArray());
     JsonParserAsync parser = new JsonParserAsync(reader);
-    String actualOne = gson.fromJson(parser.nextElement(), String.class);
+    String actualOne = gson.fromJson(parser.next(), String.class);
     assertEquals("one", actualOne);
-    String actualTwo = gson.fromJson(parser.nextElement(), String.class);
+    String actualTwo = gson.fromJson(parser.next(), String.class);
     assertEquals("two", actualTwo);
   }
   
@@ -108,10 +108,11 @@ public class ReadersWritersTest extends TestCase {
     writer.write(gson.toJson(expectedTwo).toCharArray());
     CharArrayReader reader = new CharArrayReader(writer.toCharArray());
     JsonParserAsync parser = new JsonParserAsync(reader);
-    BagOfPrimitives actualOne = gson.fromJson(parser.nextElement(), BagOfPrimitives.class);
+    BagOfPrimitives actualOne = gson.fromJson(parser.next(), BagOfPrimitives.class);
     assertEquals("one", actualOne.stringValue);
-    BagOfPrimitives actualTwo = gson.fromJson(parser.nextElement(), BagOfPrimitives.class);
+    BagOfPrimitives actualTwo = gson.fromJson(parser.next(), BagOfPrimitives.class);
     assertEquals("two", actualTwo.stringValue);
-    JsonElement jsonElement = parser.nextElement();
+    JsonElement jsonElement = parser.next();
+    assertNull(jsonElement);
   }
 }