ClassValue in Java 7

Question

While browsing the Java 7 API documentation I stumbled upon the new class java.lang.ClassValue with the following rather minimal documentation:

Lazily

Answer 1

ClassValue cache something about the class.

Here is a part of code (at Lucene 5.0 AttributeSource.java):

/** a cache that stores all interfaces for known implementation classes for performance (slow reflection) */
private static final ClassValue[]> implInterfaces = new ClassValue[]>() {
    @Override
    protected Class[] computeValue(Class clazz) {
      final Set> intfSet = new LinkedHashSet<>();
      // find all interfaces that this attribute instance implements
      // and that extend the Attribute interface
      do {
        for (Class curInterface : clazz.getInterfaces()) {
          if (curInterface != Attribute.class && Attribute.class.isAssignableFrom(curInterface)) {
            intfSet.add(curInterface.asSubclass(Attribute.class));
          }
        }
        clazz = clazz.getSuperclass();
      } while (clazz != null);
      @SuppressWarnings({"unchecked", "rawtypes"}) final Class[] a =
          intfSet.toArray(new Class[intfSet.size()]);
      return a;
    }
};