转自:https://blog.csdn.net/superit401/article/details/51727739

1.String转JSONObject

（1）.String jsonMessage = "{\"语文\":\"88\",\"数学\":\"78\",\"计算机\":\"99\"}";

JSONObject  myJson = JSONObject.fromObject(jsonMessage);

（2）.用阿里巴巴的fastjson的jar包

String str = "{\"baid\":null,\"32d3:\":\"null\",433:\"0x32\",032:\"ju9fw\"}";

com.alibaba.fastjson.JSONObject jm = com.alibaba.fastjson.JSON.parseObject(str);

2.String转JSONArray

String jsonMessage = "[{'num':'成绩', '外语':88, '历史':65, '地理':99, 'object':{'aaa':'1111','bbb':'2222','cccc':'3333'}}," +

          "{'num':'兴趣', '外语':28, '历史':45, '地理':19, 'object':{'aaa':'11a11','bbb':'2222','cccc':'3333'}}," +

          "{'num':'爱好', '外语':48, '历史':62, '地理':39, 'object':{'aaa':'11c11','bbb':'2222','cccc':'3333'}}]";

 JSONArray myJsonArray = JSONArray.fromObject(jsonMessage);

 System.out.println(myJsonArray);

3.String转Map

(1)

 

String jsonMessage = "{\"语文\":\"88\",\"数学\":\"78\",\"计算机\":\"99\"}";

JSONObject  myJson = JSONObject.fromObject(jsonMessage);

Map m = myJson; 

（2）用阿里巴巴的fastjson的jar包

String str = "{\"baid\":null,\"32d3:\":\"null\",433:\"0x32\",032:\"ju9fw\"}";

Map mapTypes = com.alibaba.fastjson.JSON.parseObject(str);

(3) (需要引入jackjson的core、databind、annotations三个jar包  )

String json = "{\"PayPal key2\":\"PayPal value2\",\"PayPal key1\":\"PayPal value1\",\"PayPal key3\":\"PayPalvalue3\"}";  

ObjectMapper mapper = new ObjectMapper();    

 Map<String,Object> m = mapper.readValue(json, Map.class);  

(4)(特殊格式的String)

 

String a ="{se=2016, format=xml, at=en co=3}";

a =  a.substring(1, a.length()-1);

Map docType = new HashMap();  

.util.StringTokenizer items;  

for(StringTokenizer entrys = new StringTokenizer(a, ", ");entrys.hasMoreTokens();   

docType.put(items.nextToken(), items.hasMoreTokens() ? ((Object) (items.nextToken())) : null)){  

     items = new StringTokenizer(entrys.nextToken(), "=");  

   }

 

4.JSONObject、JSONArray，Map转String

JSONObject——String：

System.out.println(myJsonObject);//可直接输出JSONObject的内容

myJsonObject.toString();

阿里巴巴fastjson：

String str = JSON.toJSONString(obj,SerializerFeature.BrowserCompatible);

JSONArray——String：

System.out.println(myJsonArray);//可直接输出myJsonArray的内容

myJsonArray.toString();

Map——String:

System.out.println(map);//可直接输出map的内容

map.toString();

 

5.JSONObject转JSONArray

 

 

6.JSONObject转Map

 

JSONObject  myJson = JSONObject.fromObject(jsonString);

Map m = myJson; 

 

7.JSONArray转JSONObject

 

 

  for(int i=0 ; i < myJsonArray.length() ;i++)

   {

    //获取每一个JsonObject对象

    JSONObject myjObject = myJsonArray.getJSONObject(i);

 

 

}

 

8.JSONArray转Map

 

 

9.Map转JSONObject

JSONObject json = JSONObject.fromObject( map );   

或

String jsonString = JSON.toJSONString(map,SerializerFeature.WriteMapNullValue,SerializerFeature.WriteNullStringAsEmpty);

JSONObject jm = JSON.parseObject(str);

(此为alibaba的fastjson)

 

10.Map转JSONArray

   JSONArray.fromObject(map);

11.List转JSONArray

JSONArray jsonArray2 = JSONArray.fromObject( list );      

 

12.JSONArray转List

List<Map<String,Object>> mapListJson = (List)jsonArray;

或

public static List<Map<String, Object>> jsonArrayToList(JSONArray ja){  

        return JSONArray.toJavaObject(ja, List.class);  

    } 

 

13.String转数组

String string = "a,b,c";

String [] stringArr= string.split(",");  //注意分隔符是需要转译滴...

如果是"abc"这种字符串,就直接

String string = "abc" ;

char [] stringArr = string.toCharArray(); //注意返回值是char数组

如果要返回byte数组就直接使用getBytes方法就ok了~~

String string = "abc" ;

byte [] stringArr = string.getBytes();

数组转String

char[] data={a,b,c}; 

String s=new String(data); 

 

14.java实体类的List转String

JSON与String关系比较近，而JSON的子类JSONArray又和List关系比较近，故把JSONArray做中介过渡：

import com.alibaba.fastjson.JSONArray;

public String list2str(List<?> list){

JSONArray jsonArray = (JSONArray) JSONArray.toJSON(list);   //List转JSONArray

System.out.println(jsonArray.toString());

return jsonArray.toJSONString();    //JSONArray比较容易转String

}

15.Array、List、Set之间转换：

String[] arr = new String[]{"Tom", "Bob", "Jane"};

//Array转List

List<String> arr2list = Arrays.asList(arr);

//Array转Set

Set<String> arr2set = new HashSet<String>(Arrays.asList(arr));

//List转Array

Object[] list2arr = arr2list.toArray();

//List转Set

Set<String> list2set = new HashSet<>(arr2list);

//Set转Array

Object[] set2arr = list2set.toArray();

//Set转List

List<String> set2list = new ArrayList<>(arr2set);

List<String> list = new ArrayList<String>(new HashSet<String>());//