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 w

Answer 1

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
  @SuppressWarnings("unchecked")
  private static  Class wrap(Class c) {
    return c.isPrimitive() ? (Class) PRIMITIVES_TO_WRAPPERS.get(c) : c;
  }

  private static final Map, Class> PRIMITIVES_TO_WRAPPERS
    = new ImmutableMap.Builder, 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.