Method memoize

oshi-core/src/main/java/oshi/util/Memoizer.java:73–98

Store a supplier in a delegate function to be computed once, and only again after time to live (ttl) has expired. @param The type of object supplied @param original The java.util.function.Supplier to memoize @param ttlNanos Time in nanoseconds to retain

(Supplier<T> original, long ttlNanos)

     * @return A memoized version of the supplier
     */
    public static <T> Supplier<T> memoize(Supplier<T> original, long ttlNanos) {
        // Adapted from Guava's ExpiringMemoizingSupplier
        return new Supplier<T>() {
            final Supplier<T> delegate = original;
            volatile T value; // NOSONAR squid:S3077
            volatile long expirationNanos;

            @Override
            public T get() {
                long nanos = expirationNanos;
                long now = System.nanoTime();
                if (nanos == 0 || (ttlNanos >= 0 && now - nanos >= 0)) {
                    synchronized (this) {
                        if (nanos == expirationNanos) { // recheck for lost race
                            T t = delegate.get();
                            value = t;
                            nanos = now + ttlNanos;
                            expirationNanos = (nanos == 0) ? 1 : nanos;
                            return t;
                        }
                    }
                }
                return value;
            }
        };
    }

    /**
     * Store a supplier in a delegate function to be computed only once.