Simple way to get wrapper class type in Java

Question

I have a piece of code where I need to pass the class of a field in a method. Because of the mechanics of my code I can only handle reference objects and not primitives. I want an easy way of determining if a Field's type is primitive and swap it with the appropriate wrapper class. So in code what I do so far is something like this:

Field f = getTheField(); // Dummy method that returns my Field Class<?> c = f.getType(); if (c == int.class) {     c = Integer.class; } else if (c == float.class) {     c = Float.class; } // etc myMethod(c); 

This works fine, except for the fact that I need to explicitly check for all the primitive types and swap them with the appropriate wrapper class. Now I know that there are not so many primitive types and it won't be a problem to simply list them all, but I was wondering if there was an easier and more elegant way of doing it.

Answer 1

Apache Commons Lang has a utility method to do this (ClassUtils.primitiveToWrapper()), which will be just as ugly under the covers, but at least you can pretend it's nice.

Answer 2

I use Google Collections Library in my answer, because I'm spoiled like that, but you can probably see how to do it with plain HashMaps if you prefer.

  // safe because both Long.class and long.class are of type Class<Long>   @SuppressWarnings("unchecked")   private static <T> Class<T> wrap(Class<T> c) {     return c.isPrimitive() ? (Class<T>) PRIMITIVES_TO_WRAPPERS.get(c) : c;   }    private static final Map<Class<?>, Class<?>> PRIMITIVES_TO_WRAPPERS     = new ImmutableMap.Builder<Class<?>, Class<?>>()       .put(boolean.class, Boolean.class)       .put(byte.class, Byte.class)       .put(char.class, Character.class)       .put(double.class, Double.class)       .put(float.class, Float.class)       .put(int.class, Integer.class)       .put(long.class, Long.class)       .put(short.class, Short.class)       .put(void.class, Void.class)       .build(); 

It is odd that nothing exists in the JDK for this, but indeed nothing does.

EDIT: I'd totally forgotten that we released this:

http://google.github.io/guava/releases/21.0/api/docs/com/google/common/primitives/Primitives.html

It has the wrap() method, plus unwrap() and a few other incidental things.