com.github.loki4j.client.util.Cache Maven / Gradle / Ivy

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package com.github.loki4j.client.util;

import java.util.HashMap;
import java.util.concurrent.atomic.AtomicReference;
import java.util.function.Supplier;

/**
 * A simple cache interface.
 */
public interface Cache {

    /**
     * Get the value from cache based by key.
     * @param key Key to get a value from the cache 
     * @param onMiss Supplier for a value in case it's missing in cache
     */
    V get(K key, Supplier onMiss);

    /**
     * Simple cache implementation based on atomic reference on unbound hash map.
     */
    public static class UnboundAtomicMapCache implements Cache {
        private final AtomicReference> cache = new AtomicReference<>(new HashMap<>());

        @Override
        public V get(K key, Supplier onMiss) {
            return cache
                .updateAndGet(m -> {
                    if (!m.containsKey(key)) {
                        var nm = new HashMap<>(m);
                        nm.put(key, onMiss.get());
                        return nm;
                    } else {
                        return m;
                    }
                })
                .get(key);
        }
    }
}