教你怎么编写高效的JSON工具类

package com.beichende.ibank.util;
 
import com.google.gson.Gson;
import com.google.gson.JsonArray;
import com.google.gson.JsonElement;
import com.google.gson.JsonParser;
 
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
 
import org.json.JSONArray;
import org.json.JSONObject;
 
/**
 * Description：GSON单例类，提供对象到JSON数据格式转换
 *
 * @author gujc
 */
public class JsonUtil {
    private static Gson gson = null;
 
    private JsonUtil() {
    }
 
    private static Gson gson() {
        if (gson == null) {
            synchronized (JsonUtil.class) {
                if (gson == null) {
                    gson = new Gson();
                }
            }
        }
        return gson;
    }
 
    /**
     * 目标对象到JSON数据格式转换
     *
     * @param src 目标对象
     */
    public static String toJson(Object src) {
        return gson().toJson(src);
    }
 
    /**
     * JSON格式数据到目标对象转换
     *
     * @param js    JSON格式数据
     * @param clazz 目标对象類型
     * @return 目标对象
     * @throws "JsonConvertException"
     */
    public static <T> T fromJson(String js, Class<T> clazz) {
        return gson().fromJson(js, clazz);
    }
 
    public static <T> List<T> getObjectList(String jsonString,Class<T> cls){
        List<T> list = new ArrayList<T>();
        try {
            Gson gson = new Gson();
            JsonArray arry = new JsonParser().parse(jsonString).getAsJsonArray();
            for (JsonElement jsonElement : arry) {
                list.add(gson.fromJson(jsonElement, cls));
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return list;
    }
    public static <M> List<M> getList(String jsonString,Class<M> cls){
        List<M> list = new ArrayList<M>();
        try {
            Gson gson = new Gson();
            JsonArray arry = new JsonParser().parse(jsonString).getAsJsonArray();
            for (JsonElement jsonElement : arry) {
                list.add(gson.fromJson(jsonElement, cls));
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return list;
    }
    /**
     * Json 转成 Map<>
     * @param jsonStr
     * @return
     */
    public static Map<String, Object> getMapForJson(String jsonStr){
        JSONObject jsonObject ;
        try {
            jsonObject = new JSONObject(jsonStr);
 
            Iterator<String> keyIter= jsonObject.keys();
            String key;
            Object value ;
            Map<String, Object> valueMap = new HashMap<String, Object>();
            while (keyIter.hasNext()) {
                key = keyIter.next();
                value = jsonObject.get(key);
                valueMap.put(key, value);
            }
            return valueMap;
        } catch (Exception e) {
            // TODO: handle exception
            e.printStackTrace();
        }
        return null;
    }
    /**
     * Json 转成 List<Map<>>
     * @param jsonStr
     * @return
     */
    public static List<Map<String, Object>> getlistForJson(String jsonStr){
        List<Map<String, Object>> list = null;
        try {
            JSONArray jsonArray = new JSONArray(jsonStr);
            JSONObject jsonObj ;
            list = new ArrayList<Map<String,Object>>();
            for(int i = 0 ; i < jsonArray.length() ; i ++){
                jsonObj = (JSONObject)jsonArray.get(i);
                list.add(getMapForJson(jsonObj.toString()));
            }
        } catch (Exception e) {
            // TODO: handle exception
            e.printStackTrace();
        }
        return list;
    }
    public static <T> boolean isEmpty(List<T> sourceList) {
        return (sourceList == null || sourceList.size() == 0);
    }
    /**
     * 输入流转字符串
     * @param is
     * @return
     */
    public  static String convertStreamToString(InputStream is) {
 
        BufferedReader reader = new BufferedReader(new InputStreamReader(is));
        StringBuilder sb = new StringBuilder();
        String line = null;
        try {
            while ((line = reader.readLine()) != null) {
                sb.append(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                is.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return sb.toString();
 
    }
}

public class Student {
  private String name;
  private String sex;
  private String age;
  private String address;
  
  public Student() {
    
  }
  
  public Student(String name, String sex, String age, String address) {
    super();
    this.name = name;
    this.sex = sex;
    this.age = age;
    this.address = address;
  }
  public String getName() {
    return name;
  }
  public void setName(String name) {
    this.name = name;
  }
  public String getSex() {
    return sex;
  }
  public void setSex(String sex) {
    this.sex = sex;
  }
  public String getAge() {
    return age;
  }
  public void setAge(String age) {
    this.age = age;
  }
  public String getAddress() {
    return address;
  }
  public void setAddress(String address) {
    this.address = address;
  }
  
}

public class StudentCount {
  private String count;
  private List<Student> list;
  public String getCount() {
    return count;
  }
  public void setCount(String count) {
    this.count = count;
  }
  public List<Student> getList() {
    return list;
  }
  public void setList(List<Student> list) {
    this.list = list;
  }
  
}