Android学习记录045

class GenericType {
    private T data;

    public void setData(T data) {
        this.data = data;
    }

    public T getData() {
        return data;
    }
}

//这种方式定义泛型变量，要想通过操作appleGenericType.getClass()是无法获取到泛型的真实类型的
//因为在运行的时候泛型类中的泛型已经被擦除了
GenericType appleGenericType = new GenericType();

	
    GenericType appleGenericType = new GenericType();
    appleGenericType.setData(new Apple());
    Method method = appleGenericType.getClass().getMethod("getData");
    Object invoke = method.invoke(appleGenericType);
    System.out.println(invoke.getClass());//class generically.Apple

GenericType appleGenericType = new GenericType(){};
Class appleGenericTypeClass = appleGenericType.getClass();
Type appleGenericSuperclass = appleGenericTypeClass.getGenericSuperclass();
System.out.println(((ParameterizedType)appleGenericSuperclass).getRawType()); //class generically.GenericType
System.out.println(appleGenericSuperclass.getTypeName());//generically.GenericType
System.out.println(((ParameterizedType)appleGenericSuperclass).getActualTypeArguments()[0]);//class generically.Apple

    interface ReturnType{
         GenericType getApple();
    }

 Method getAppleMethod = ReturnType.class.getMethod("getApple");
 Type genericReturnType = getAppleMethod.getGenericReturnType();
 System.out.println(genericReturnType);//generically.GenericType
 System.out.println(genericReturnType instanceof ParameterizedType); //true
 ParameterizedType parameterizedType = (ParameterizedType) genericReturnType;
 System.out.println(parameterizedType.getActualTypeArguments()[0]); //class generically.Apple
 System.out.println(parameterizedType.getOwnerType()); //null
 System.out.println(parameterizedType.getRawType());//class generically.GenericType
System.out.println(parameterizedType.getTypeName());//generically.GenericType

 
  List arrayList = new ArrayList(){};
  Type type = arrayList.getClass().getGenericSuperclass();
  ParameterizedType parameterizedType = (ParameterizedType) type;
  System.out.println((parameterizedType.getActualTypeArguments()[0]).getTypeName()); // java.lang.Integer

ArrayList stringArrayList = new ArrayList<>();
stringArrayList.add("苹果");
 stringArrayList.add("凤梨");
 stringArrayList.add("香蕉");
 Class stringArrayListClass = stringArrayList.getClass();
 Method addMethod = stringArrayListClass.getMethod("add", Object.class);
 //通过反射给集合添加元素，这种调用方式又进一步证明了泛型的擦除
 addMethod.invoke(stringArrayList,new int[]{1,2,3});
 System.out.println(stringArrayList);
 for (int i = 0; i < stringArrayList.size(); i++) {
     Object object = stringArrayList.get(i);
    if(object.getClass().getTypeName().equals(String.class.getTypeName())){
        System.out.println(object);
    }else if(object.getClass().getTypeName().equals(int[].class.getTypeName())){
        System.out.println(object);
    }
 }