$arr = array(
  "demo1" => "my demo1",
  "demo2" => array(
    "demo2_demo1"=>"aaaaaaaa",
    "demo2_demo2"=>"bbbbbbbb", 
    "demo2_demo3"=>array(
      "demo2_demo3_demo1"=>"ccccccc"
    )
  ),
  "demo3" => 22
);
$json_str = json_encode($arr,true);
$arr = json_decode($json_str,true);
var_dump($json_str);
var_dump($arr);
//查看結果

package Main;
import net.sf.json.JSONObject;
import net.sf.json.JSONArray;
import java.util.Map;
import java.util.HashMap;
import java.util.List;
import java.util.ArrayList;
import Main.Demo1;
public class Index 
{
  public static void main(String[] args)
  {
    index4();
  }
  /**
   * 簡單的simple
   * */
  public static void index1()
  {
    JSONObject json = new JSONObject();
    json.element("name","譚勇");
    json.element("age",22);
    System.out.println(json.toString());
  }
  /**
   * Map 數據轉json
   * */
  public static void index2()
  {
    JSONObject json = new JSONObject();
    MapString,String> map = new HashMapString,String>();
    map.put("name", "譚勇");
    map.put("age", "22");
    json.accumulateAll(map);
    System.out.println(json.toString());
  }
  /**
   * ListMap> 轉json
   * */
  public static void index3()
  {
    JSONArray arr = new JSONArray();
    ListMapString,String>> list = new ArrayListMapString,String>>();
    list.add(getMap("name","譚勇"));
    list.add(getMap("age","22"));
    arr.addAll(list);
    System.out.println(arr.toString());
  }
  /**
   * 對象轉Json
   * */
  public static void index4()
  {
    Demo1 demo1 = new Demo1();
    demo1.setName("譚勇");
    demo1.setAge(22);
    JSONObject json = new JSONObject();
    JSONArray arr = new JSONArray();
    json.element("demo1",demo1);
    arr.add(demo1);
    //json.containsKey(demo1);
    System.out.println(json.toString());
    System.out.println(arr.toString());
  }
  private static MapString,String> getMap(String key,String val)
  {
    MapString,String> map = new HashMapString,String>();
    map.put(key, val);
    return map;
  }
}

package Main;
public class Demo1 
{
  private String name;
  private int age;
  public void setName(String name)
  {
    this.name = name;
  }
  public String getName()
  {
    return this.name;
  }
  public void setAge(int age)
  {
    this.age = age;
  }
  public int getAge()
  {
    return this.age;
  }
}