/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.jena.atlas.lib.cache ;

import java.util.Iterator ;
import java.util.concurrent.Callable ;
import java.util.function.BiConsumer;

import org.apache.jena.atlas.iterator.Iter ;
import org.apache.jena.atlas.lib.Cache ;

/** A cache that keeps nothing */
public final class Cache0<K, V> implements Cache<K, V> {
    @Override
    public boolean containsKey(K key) {
        return false ;
    }

    @Override
    public V getIfPresent(K key) {
        return null ;
    }

    @Override
    public V getOrFill(K key, Callable<V> callable) {
        return null ;
    }

    @Override
    public void put(K key, V thing) {}

    @Override
    public void remove(K key) {}

    @Override
    public Iterator<K> keys() {
        return Iter.nullIterator() ;
    }

    @Override
    public boolean isEmpty() {
        return true ;
    }

    @Override
    public void clear() {}

    @Override
    public long size() {
        return 0 ;
    }

    @Override
    public void setDropHandler(BiConsumer<K, V> dropHandler) {}

}

@@ -1361,37 +1361,174 @@
 ) %7B%0A        
-return null ;
+try %7B%0A            return callable.call() ;%0A        %7D%0A        catch (Exception e) %7B%0A            e.printStackTrace();%0A            return null;%0A        %7D
 %0A    %7D%0A%0A    

Make Cache0.getOrFill always calculate and return the value.