ClassUtils.java

package silentium.commons.utils;

import com.google.common.base.Preconditions;

/**
 * This class contains utilities that are used when we are working with classes
 *
 * @author SoulKeeper
 */
public class ClassUtils {
	/**
	 * Return true if class a is either equivalent to class b, or if class a is a subclass of class b, i.e. if a either
	 * "extends" or "implements" b. Note tht either or both "Class" objects may represent interfaces.
	 *
	 * @param a class
	 * @param b class
	 * @return true if a == b or a extends b or a implements b
	 */
	public static boolean isSubclass(final Class<?> a, final Class<?> b) {
		// We rely on the fact that for any given java class or
		// primtitive type there is a unqiue Class object, so
		// we can use object equivalence in the comparisons.
		if (a == b)
			return true;

		Preconditions.checkNotNull(a);
		Preconditions.checkNotNull(b);

		for (Class<?> x = a; x != null; x = x.getSuperclass()) {
			if (x == b)
				return true;

			if (b.isInterface()) {
				final Class<?>[] interfaces = x.getInterfaces();

				for (final Class<?> anInterface : interfaces)
					if (isSubclass(anInterface, b))
						return true;
			}
		}

		return false;
	}
}