Class＃isAssignableFrom和unboxing / boxing

Question

As we know, Class#isAssignable does not consider, that a value can be auto boxed/unboxed. Eg the lower of the four following cases return false :

// obvious
System.out.println(boolean.class.isAssignableFrom(boolean.class)); // true
System.out.println(Boolean.class.isAssignableFrom(Boolean.class)); // true


// boxing/unboxing
System.out.println(boolean.class.isAssignableFrom(Boolean.class)); // false
System.out.println(Boolean.class.isAssignableFrom(boolean.class)); // false

Is there a pre-existing variant of this method which would consider this case? (ie returning true in all four given cases above.) If not, what would be the best way of implementing this for all primitive/wrapped combinations?

Answer 1

这个方法是关于子类型的，而不是一个值是否可以分配给变量，这要复杂得多，请参阅http://docs.oracle.com/javase/specs/jls/se7/html/jls-5.html# JLS-5.2

Answer 2

I have a WRAPPER_MAP field like this.

WRAPPER_MAP.put(boolean.class, Boolean.class);
// add others

then I look this up.

public static Class wrap(Class clazz) {
     Class clazz2 = WRAPPER_MAP.get(clazz);
     return clazz2 == null ? clazz : clazz2;
}

Then the test is

wrap(clazz1).isAssignableFrom(wrap(clazz2));