Java抽象类型类编译时间检查

Question

Is it possible somehow to check at COMPILE time do classType points to an abstract type? Runtime check can be done:

void foo(Class<? extends SubType> classType) {
    Modifier.isAbstract(classType.getModifiers()); 
}

foo(AbstractType.class);    // this should pass
foo(NotAbstractType.class); // this should fail

If same could be done at COMPILE time?

Answer 1

You could write your own @MustBeAbstract annnotation and then an annnotation processor that enforces that any class with that annnotation is abstract.

See this question on annnotation processing: What is annotation processing in Java?

Answer 2

To my knowledge, there is no automatic solution.

However, if you know in advance the list of classes that are passed to method foo, you can implement a manual solution. ie

private ArrayList<Class> abstractTypes = new ArrayList<>();

void foo(Class<? extends SubType> classType) {
    boolean isAbstract = false;
    for(Class c: abstractTypes)
       if((classType.getName()).equals(c.getName()){
          isAbstract = true;
          break;
       }

    //Do something else...   
}