Example：

拼一个如下的json格式String

{
    [
        {
            "id": 912345678901,
            "text": "How do I write JSON on Android?",
            "geo": null,
            "user": {
                "name": "android_newb",
                "followers_count": 41
            }
        },
        {
            "id": 912345678902,
            "text": "@android_newb just use android.util.JsonWriter!",
            "geo": [
                50.454722,
                -104.606667
            ],
            "user": {
                "name": "jesse",
                "followers_count": 2
            }
        }
    ]
}

关键代码：

 public static String writeJsonStream(List<Message> messages)throwsIOException{

　　if(messages!=null && messages.size() > 0){

　　　　ByteArrayOutputStream out = new ByteArrayOutputStream();
           JsonWriter writer = new JsonWriter(new OutputStreamWriter(out, "UTF-8"));

　　　 writer.setIndent("");

　　　 writeMessagesArray(writer, messages);     　writer.close();

　　　 byte[] bytes = out.toByteArray();       return new String(bytes);

　　}
     return null;

}

private static void writeMessagesArray(JsonWriter writer,List messages)throwsIOException{
     writer.beginArray();
     for(Message message : messages){
       writeMessage(writer, message);
     }
     writer.endArray();

}

private static void writeMessage(JsonWriter writer,Message message)throwsIOException{     writer.beginObject();     writer.name("id").value(message.getId());     writer.name("text").value(message.getText());     if(message.getGeo()!=null){       writer.name("geo");       writeDoublesArray(writer, message.getGeo());     }else{       writer.name("geo").nullValue();     }     writer.name("user");     writeUser(writer, message.getUser());     writer.endObject();}

private static void writeUser(JsonWriter writer,User user)throwsIOException{     writer.beginObject();     writer.name("name").value(user.getName());     writer.name("followers_count").value(user.getFollowersCount());     writer.endObject();}

 private static void writeDoublesArray(JsonWriter writer,List doubles)throwsIOException{     writer.beginArray();     for(Double value : doubles){       writer.value(value);     }     writer.endArray(); }