Java Class.isAssignableFrom confusion

Question

I find primitive type problem

System.out.println("Integer.class.isAssignableFrom(int.class) = " + Integer.class.isAssignableFrom(int.class));
System.out.println("int.class.isAssignableFrom(Integer.class) = "+int.class.isAssignableFrom(Integer.class));

both of the statements return false to the caller. so that seems like boxing is not applicable here. My question is if my observation is correct or there are other API who can do this testing correctly?

--------------------------------following up---------------------------------------------

As I said, I mainly want to check if a Object is assignable to a Field when using reflection. I hope the mechanism could be more precise at run time so I made a implementation like this.

    public static boolean isAssignableFrom(final Field field, final Object obj) {


        if (field.getType().equals(Integer.class) || field.getType().equals(int.class)) {
            return obj.getClass().equals(Integer.class) || field.getType().equals(int.class);
        } else if (field.getType().equals(Float.class) || field.getType().equals(float.class)) {
            return obj.getClass().equals(Float.class) || field.getType().equals(float.class);
        } else if (field.getType().equals(Double.class) || field.getType().equals(double.class)) {
            return obj.getClass().equals(Double.class) || field.getType().equals(double.class);
        } else if (field.getType().equals(Character.class) || field.getType().equals(char.class)) {
            return obj.getClass().equals(Character.class) || field.getType().equals(char.class);
        } else if (field.getType().equals(Long.class) || field.getType().equals(long.class)) {
            return obj.getClass().equals(Long.class) || field.getType().equals(long.class);
        } else if (field.getType().equals(Short.class) || field.getType().equals(short.class)) {
            return obj.getClass().equals(Short.class) || field.getType().equals(short.class);
        } else if (field.getType().equals(Boolean.class) || field.getType().equals(boolean.class)) {
            return obj.getClass().equals(Boolean.class) || field.getType().equals(boolean.class);
        } else if (field.getType().equals(Byte.class) || field.getType().equals(byte.class)) {
            return obj.getClass().equals(Byte.class) || field.getType().equals(byte.class);
        }
        return field.getType().isAssignableFrom(obj.getClass());
    }

}

That seems the best I can do -_-! thanks

Answer 1

I suppose, ClassUtils.isAssignable(Class, Class, boolean) from Apache commons-lang is the one to help.

JavaDoc

Answer 2

int.class and Integer.class are two separate class objects. check this answer for more details

From Java doc Class#isAssignableFrom

Determines if the class or interface represented by this Class object is either the same as, or is a superclass or superinterface of, the class or interface represented by the specified Class parameter. It returns true if so; otherwise it returns false. If this Class object represents a primitive type, this method returns true if the specified Class parameter is exactly this Class object; otherwise it returns false.