- **I/O Operations** (`org.codelibs.core.io`) - File handling, resource management, stream utilities, and traversal utilities for efficient resource processing
- **Reflection** (`org.codelibs.core.lang`) - Class loading, method/field access, type introspection utilities, and generics support

    TypeVariableImpl<D> typeVariableImpl = new TypeVariableImpl<>(genericDeclaration, name, bounds);
    @SuppressWarnings("unchecked")
    TypeVariable<D> typeVariable =
        Reflection.newProxy(
            TypeVariable.class, new TypeVariableInvocationHandler(typeVariableImpl));
    return typeVariable;
  }

  /**

        // We can't directly test ProcessDestroyer without creating actual processes,
        // but we can test that the class exists and basic functionality
        try {
            // Use reflection to verify ProcessDestroyer class exists
            final Class<?> destroyerClass = Class.forName("org.codelibs.fess.thumbnail.impl.CommandGenerator$ProcessDestroyer");

    /*
     * We'd use assertThrows here, but that causes no exception to be thrown under Java 8,
     * presumably because the ThrowingRunnable lambda triggers some kind of bug in Java 8's
     * reflection implementation.
     */
    try {
      new TypeToken<T>() {};
      fail();
    } catch (IllegalStateException expected) {
      // Type variables aren't allowed.
    }
  }

    /*
     * We'd use assertThrows here, but that causes no exception to be thrown under Java 8,
     * presumably because the ThrowingRunnable lambda triggers some kind of bug in Java 8's
     * reflection implementation.
     */
    try {
      new TypeToken<T>() {};
      fail();
    } catch (IllegalStateException expected) {
      // Type variables aren't allowed.
    }
  }

    TypeVariableImpl<D> typeVariableImpl = new TypeVariableImpl<>(genericDeclaration, name, bounds);
    @SuppressWarnings("unchecked")
    TypeVariable<D> typeVariable =
        Reflection.newProxy(
            TypeVariable.class, new TypeVariableInvocationHandler(typeVariableImpl));
    return typeVariable;
  }

  /**

        return count;
    }

    /**
     * Deletes documents in an index matching a query.
     *
     * @param index        the index name
     * @param queryBuilder the query to match documents for deletion
     * @return the number of documents deleted
     */
    public long deleteByQuery(final String index, final QueryBuilder queryBuilder) {

        final FessConfig fessConfig = ComponentUtil.getFessConfig();