Google Gson in a nutshell

JsonObject vs JsonArray

Create a JsonObject

JsonObject jo = new JsonObject();
jo.addProperty("url", url);
jo.addProperty("type", "source");
ja.add(jo);

Create a JsonArray

JsonArray ja= new JsonArray();
JsonObject jo1 = new JsonObject();
jo1.addProperty("key", "key1");
jo1.addProperty("value", "value1");
ja.add(jo1);
JsonObject jo2 = new JsonObject();
jo2.addProperty("key", "key2");
jo2.addProperty("value", "value2");
ja.add(jo2);

Iterate / Loop through all JsonObjects inside a JsonObject

Map<String, Object> attributes = new HashMap<String, Object>();
Set<Entry<String, JsonElement>> entrySet = jsonObject.entrySet();
for (Map.Entry<String, JsonElement> entry : entrySet) {
   System.out.println("Key: " + entry.getKey());
   JsonObject item = jsonObject.get(entry.getKey()).getAsJsonObject(); 
}

Iterate / Loop through all JsonElements inside a JsonArray

for (JsonElement oneElement : ja) {
   JsonObject jo = oneElement.getAsJsonObject();

}

Parse String into JsonObject

String json = "{ \"name\": \"Herwart\", \"value\": true }";
JsonObject jsonObject = JsonParser.parseString(json).getAsJsonObject();

Add a list of strings

public static void Add(JsonObject jo, String property, List<String> values) {
        JsonArray array = new JsonArray();
        for (String value : values) {
            array.add(new JsonPrimitive(value));
        }
        jo.add(property, array);
    }

Parse from json file

FileReader fr = new FileReader(filename);
Object obj = JsonParser.parseReader(fr).getAsJsonObject();

Get info from object

String start = jo.get("start").getAsString();

Print out json

Compact print

String[] lang = {"Java", "PHP"};
Gson gson = new Gson();
String json = gson.toJson(lang);

Pretty print

String[] lang = {"Java", "PHP"};

Gson gson = new GsonBuilder().setPrettyPrinting().create();
String json = gson.toJson(lang);

System.out.println(json);