java util - json转换工具 gson

package cn.java.gson;

import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;

public class Test {

    public static void main(String[] args) {
        dataType();
        dataObj();
        dataArray();
    }

    public static void dataType() {
        String jsonStr = "{\"code\":200,\"message\":\"message\",\"data\":[]}";
        JsonObject jsonObject = (JsonObject) new JsonParser().parse(jsonStr);
        System.out.println(jsonObject.get("code"));
        System.out.println(jsonObject.get("message").toString());
        System.out.println(jsonObject.get("message").getAsString());
        String dataStr = jsonObject.get("data").toString();
        if ( "{}".equals(dataStr) || "[]".equals(dataStr) || ("" == dataStr)) {
            System.out.println("data is empty..");
        }
    }

    public static void dataObj() {
        String jsonStr = "{\"code\":2,\"message\":2,\"data\":{}}";
        JsonObject jsonObject = (JsonObject) new JsonParser().parse(jsonStr);
        for (java.util.Map.Entry<String, JsonElement> entry : jsonObject.entrySet()) {
            System.out.print(entry.getKey() + "=" + entry.getValue() + "\t");
        }
        System.out.println();
    }

    public static void dataArray() {
        String jsonStr = "{\"code\":2,\"message\":2,\"data\":[]}";
        JsonObject jsonObject = (JsonObject) new JsonParser().parse(jsonStr);
        for (java.util.Map.Entry<String, JsonElement> entry : jsonObject.entrySet()) {
            System.out.print(entry.getKey() + "=" + entry.getValue() + "\t");
        }
        System.out.println();
    }

}

200
"message"
message
data is empty..
code=2    message=2    data={}    
code=2    message=2    data=[]