通过枚举实现单例模式

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.text.MessageFormat;
import java.util.Locale;

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

public enum JsonFileUtil {
    INSTANCE;
    
    private static final String imgPathFormat = "/image-generation-sample-{0}.json";
    private static final String pdfPathFormat = "/pdf-generation-sample-{0}.json";
    private static final String imgFileType = "img";
    private static final String pdfFileType = "pdf";
    
    private JsonParser jsonParser = new JsonParser();
    
    private final JsonObject jsonObject_zhcn_pdf;
    private final JsonObject jsonObject_zhtw_pdf;
    private final JsonObject jsonObject_us_pdf;
    
    private final JsonObject jsonObject_zhcn_img;
    private final JsonObject jsonObject_zhtw_img;
    private final JsonObject jsonObject_us_img;
    
    private JsonFileUtil() {
        jsonObject_zhcn_pdf = getInitedJsonObject(Locale.SIMPLIFIED_CHINESE, pdfFileType);
        jsonObject_zhtw_pdf = getInitedJsonObject(Locale.TRADITIONAL_CHINESE, pdfFileType);
        jsonObject_us_pdf = getInitedJsonObject(Locale.US, pdfFileType);
        
        jsonObject_zhcn_img = getInitedJsonObject(Locale.SIMPLIFIED_CHINESE, imgFileType);
        jsonObject_zhtw_img = getInitedJsonObject(Locale.TRADITIONAL_CHINESE, imgFileType);
        jsonObject_us_img = getInitedJsonObject(Locale.US, imgFileType);
    }
    
    private JsonObject _retriveJsonObject(Locale locale, String fileType) {
        JsonObject jsonObject = null;
        String pathFormat = null;
        
        if (fileType == "pdf")
            pathFormat = pdfPathFormat;
        else if (fileType == "img")
            pathFormat = imgPathFormat;
        
        String jsonPath = retrivejsonFilePath(pathFormat, locale);
        
        InputStream jsonIs = this.getClass().getResourceAsStream(jsonPath);
        BufferedReader jsonReader = new BufferedReader(new InputStreamReader(jsonIs));
        JsonElement jsonElement = jsonParser.parse(jsonReader);
        jsonObject = jsonElement.getAsJsonObject();
        
        return jsonObject;
    }
    
    private JsonObject getInitedJsonObject(Locale locale, String fileType) {
        JsonObject jsonObject = null;
        if (Locale.US == locale) {
            if (fileType == imgFileType) {
                if (null != jsonObject_us_img)
                    jsonObject = jsonObject_us_img;
                else
                    jsonObject = _retriveJsonObject(Locale.US, imgFileType);
            } else if (fileType == pdfFileType) {
                if (null != jsonObject_us_pdf)
                    jsonObject = jsonObject_us_pdf;
                else
                    jsonObject = _retriveJsonObject(Locale.US, pdfFileType);
            }
        } else if (Locale.SIMPLIFIED_CHINESE == locale) {
            if (fileType == imgFileType) {
                if (null != jsonObject_zhcn_img)
                    jsonObject = jsonObject_zhcn_img;
                else
                    jsonObject = _retriveJsonObject(Locale.SIMPLIFIED_CHINESE, imgFileType);
            } else if (fileType == pdfFileType) {
                if (null != jsonObject_zhcn_pdf)
                    jsonObject = jsonObject_zhcn_pdf;
                else
                    jsonObject = _retriveJsonObject(Locale.SIMPLIFIED_CHINESE, pdfFileType);
            }
        } else if (Locale.TRADITIONAL_CHINESE == locale) {
            if (fileType == imgFileType) {
                if (null != jsonObject_zhtw_img)
                    jsonObject = jsonObject_zhtw_img;
                else
                    jsonObject = _retriveJsonObject(Locale.TRADITIONAL_CHINESE, imgFileType);
            } else if (fileType == pdfFileType) {
                if (null != jsonObject_zhtw_pdf)
                    jsonObject = jsonObject_zhtw_pdf;
                else
                    jsonObject = _retriveJsonObject(Locale.TRADITIONAL_CHINESE, pdfFileType);
            }
        }
        
        return jsonObject;
    }
    
    private String retrivejsonFilePath(String formatPath, Locale locale) {
        String language = "en_US";
        if (Locale.TRADITIONAL_CHINESE.equals(locale))
            language = "zh_CN";
        else if (Locale.SIMPLIFIED_CHINESE.equals(locale))
            language = "zh_TW";
        String jsonPath = MessageFormat.format(formatPath, language);
        
        return jsonPath;
    }
    
    public JsonObject retriveJsonObject(Locale locale, String fileType) {
        return getInitedJsonObject(locale, fileType);
    }
}