如何将一个java对象(包括java对象数组、集合)转换成一个json字符串

1. package test;
2. import java.util.ArrayList;
3. import java.util.List;
4. import net.sf.json.JSONArray;
5. import net.sf.json.JSONObject;
6. import bean.Option;
8. publicclassTest {
9.     
10.     /**
11.      * Java对象 -> JSON字符串
12.      */
13.     publicstaticvoidtest1(){
14.         //{"cityName":"海淀","cityValue":"hd"}
15.         Optionop = new Option("海淀","hd");
16.         JSONObjectobj = JSONObject.fromObject(op);
17.         Stringstr = obj.toString();
18.         System.out.println(str);
19.     }
20.     
21.     /**
22.      * 数组对象 -> JSON字符串
23.      */
24.     publicstaticvoidtest2(){
25.         //[{"cityName":"海淀","cityValue":"hd"},...]
26.         Optionop = new Option("海淀","hd");
27.         Optionop2 = new Option("东城","dc");
28.         Optionop3 = new Option("西城","xc");
29.         Option[] ops= {op,op2,op3};
30.         JSONArrayobj = JSONArray.fromObject(ops);
31.         Stringstr = obj.toString();
32.         System.out.println(str);
33.     }
34.     
35.     /**
36.      * List对象 -> JSON字符串
37.      */
38.     publicstaticvoidtest3(){
39.         //[{"cityName":"海淀","cityValue":"hd"},...]
40.         Optionop = new Option("海淀","hd");
41.         Optionop2 = new Option("东城","dc");
42.         Optionop3 = new Option("西城","xc");
43.         List<Option>ops = new ArrayList<Option>();
44.         ops.add(op);
45.         ops.add(op2);
46.         ops.add(op3);
47.         JSONArrayobj = JSONArray.fromObject(ops);
48.         Stringstr = obj.toString();
49.         System.out.println(str);
50.     }
51.     
52.     publicstaticvoidmain(String[] args){
53.         test1();
54. test2();
55. test3();
56.     }
57. }