import java.util.HashMap;
import java.util.Map;
import net.sf.json.JSONObject;

public class testJson {
 
    public static void main(String[] args) {
        testPingping();
    }
    public static void testPingping(){ 
        Map<String, String> smallMap = new HashMap<String, String>(); 
        smallMap.put(
 
"userId", "438");
        smallMap.put("name", "平平/萍萍");
        smallMap.put("sex", "不知男女");
        smallMap.put("reason", "和學成睡一晚，後來學成嘴疼"); 
    JSONObject jsonObject = JSONObject.fromObject(smallMap);
    System.out.println("下面是專家開具的鑒定結果："); //A joke
    System.out.println(jsonObject);
    System.out.println(
 
"患者鑒定完畢！"); //A joke
    System.out.println("下一位"); //A joke

    } 
}

也可以是Map<String, Object>類型

輸出的結果：

下面是結果：
{"b_name":"平平/萍萍","d_reason":"和學成睡一晚，後來學成嘴疼","a_userId":"438","c_sex":"不知男女"}

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需要引入的jar包列表：

cglib-nodep-2.2.jar
commons-beanutils-1.8.0.jar
commons-collections-3.2.1.jar
commons-lang-2.4.jar
commons-logging-1.1.1.jar
ezmorph-1.0.4.jar
gson-2.8.0-javadoc.jar
gson-2.8.0-sources.jar
gson-2.8.0.jar
jettison-1.3.1.jar
json-lib-2.2.1-jdk13.jar
json.jar

Map<String,String>轉換json字符串