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Java Reflection - How to find out by reflection that a primitive class is assignable to/from its corresponding wrapper class?

Java Reflection Java 

Class.isAssignable() returns false if we use it for a primitive class and pass its corresponding wrapper class (or vice-versa). They are, in fact, assignable to each other via auto boxing/unboxing.
Following utility method isAssignableTo() can handle that case too. 

import java.util.Map;

public class ReflectUtil {
    private static final Map<Class<?>, Class<?>> primitiveWrapperMap =
            Map.of(boolean.class, Boolean.class,
                    byte.class, Byte.class,
                    char.class, Character.class,
                    double.class, Double.class,
                    float.class, Float.class,
                    int.class, Integer.class,
                    long.class, Long.class,
                    short.class, Short.class);

    public static boolean isPrimitiveWrapperOf(Class<?> targetClass, Class<?> primitive) {
        if (!primitive.isPrimitive()) {
            throw new IllegalArgumentException("First argument has to be primitive type");
        }
        return primitiveWrapperMap.get(primitive) == targetClass;
    }

    private static boolean isAssignableTo(Class<?> from, Class<?> to) {
        if (to.isAssignableFrom(from)) {
            return true;
        }
        if (from.isPrimitive()) {
            return isPrimitiveWrapperOf(to, from);
        }
        if (to.isPrimitive()) {
            return isPrimitiveWrapperOf(from, to);
        }
        return false;
    }

    public static void main(String[] args) {
        boolean b = boolean.class.isAssignableFrom(Boolean.class);
        System.out.println(b);
        b = Boolean.class.isAssignableFrom(boolean.class);
        System.out.println(b);
        b = isAssignableTo(boolean.class, Boolean.class);
        System.out.println(b);
        b = isAssignableTo(Boolean.class, boolean.class);
        System.out.println(b);
    }
}

Output

false
false
true
true

See Also