void testTypeReference() {List<Integer> list = new ArrayList<>();list.add(1);list.add(9);list.add(4);list.add(8);JSONObject jsonObj = new JSONObject();jsonObj.put("a", list);System.out.println(jsonObj);List<String> list2 = jsonObj.getObject("a", new TypeReference<List<Integer>>(){});System.out.println(list2);}

{"a":[1,9,4,8]}
[1, 9, 4, 8]

  protected TypeReference(){Type superClass = getClass().getGenericSuperclass();Type type = ((ParameterizedType) superClass).getActualTypeArguments()[0];Type cachedType = classTypeCache.get(type);if (cachedType == null) {classTypeCache.putIfAbsent(type, type);cachedType = classTypeCache.get(type);}this.type = cachedType;}

package JsonLearn;import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.HashMap;
import java.util.Map;public class TypeReferencBaseLearn {public static class IntMap extends HashMap<String, Integer> {}void test1() {IntMap intMap = new IntMap();System.out.println("getSuperclass:" + intMap.getClass().getSuperclass());System.out.println("getGenericSuperclass:" + intMap.getClass().getGenericSuperclass());Type type = intMap.getClass().getGenericSuperclass();if (type instanceof ParameterizedType) {ParameterizedType p = (ParameterizedType)type;for (Type t : p.getActualTypeArguments()) {System.out.println(t);}}}void test2() {Map<String, Integer> intMap = new HashMap<>();System.out.println("\ngetSuperclass:" + intMap.getClass().getSuperclass());System.out.println("getGenericSuperclass:" + intMap.getClass().getGenericSuperclass());Type type = intMap.getClass().getGenericSuperclass();if (type instanceof ParameterizedType) {ParameterizedType p = (ParameterizedType)type;for (Type t : p.getActualTypeArguments()) {System.out.println(t);}}}void test3() {Map<String, Integer> intMap = new HashMap<String, Integer>(){};System.out.println("\ngetSuperclass:" + intMap.getClass().getSuperclass());System.out.println("getGenericSuperclass:" + intMap.getClass().getGenericSuperclass());Type type = intMap.getClass().getGenericSuperclass();if (type instanceof ParameterizedType) {ParameterizedType p = (ParameterizedType)type;for (Type t : p.getActualTypeArguments()) {System.out.println(t);}}}public static void main(String[] args) {TypeReferencBaseLearn obj = new TypeReferencBaseLearn();obj.test1();obj.test2();obj.test3();}
}

getSuperclass:class java.util.HashMap
getGenericSuperclass:java.util.HashMap<java.lang.String, java.lang.Integer>
class java.lang.String
class java.lang.IntegergetSuperclass:class java.util.AbstractMap
getGenericSuperclass:java.util.AbstractMap<K, V>
K
VgetSuperclass:class java.util.HashMap
getGenericSuperclass:java.util.HashMap<java.lang.String, java.lang.Integer>
class java.lang.String
class java.lang.Integer　

Map<String, Integer> intMap = new HashMap<String, Integer>(){};

Map<String, Integer> intMap = new HashMap<String, Integer>;